INDIAN INSTITUTE OF TECHNOLOGY KANPUR Centre for Nanotechnology Initiative

Internal Review Meeting

PBCEC, IIT Kanpur

May 10, 2008

1

1 Vision, Mission, Strategies & Objectives of the Centre 03

2 Organizational Structure, Personnel & Budget 06

3 Significant Achievements : 10

4 Nanostructures and Nanomaterials for Printable Electronics 11

5 Financial Status: 31

6 SPACE, PEOPLE, FACILITIES, ACTIVITIES 32

7 CONCLUDING REMARKS 33

Abstract In order to derive concrete product prototypes using nanosceince and technology, a

unique project, funded by nanotechnology initiative of DST, has been initiated at a

current total outlay of 11.5 crores from January 2007. The project focus is currently in

the inter-related areas of : Development of Printable Organic Electronics with Organic-

RFID tags as the first demonstrator prototype, and the Development of a versatile

focused ion beam tool based on microwave plasma ion beam for applications in

patterning and templating of soft-materials and substrates. As a part of this project world

class facilities for printing circuits with technologies such as ink-jet, nano-stamping and

gravure printing methods will be installed.

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Development of Printable Organic Electronics

There have been significant progress in design and fabrication of ‘Organic Thin Film

Transistors’ with different architectures. Both top gate and bottom gate TFTs have been

fabricated and tested using existing facilities. Composite and multilayered dielectrics

have been employed in the fabrication of Organic Thin Film Transistors. The channel

current measured in these devices is very encouraging and demonstrate their potential

use in organic electronic circuits. Work is also under progress to design nanoscale

organic thin film transistors using focused ion beam to carve out nanoelectrodes. The

ability to manipulate and make electrical measurements at a nanoscale is also an

integral part. There have been under this project significant progress in the design and

fabrication of ‘Organic Thin Film Transistors’ with different architectures.. Simulational

tools needed for design of components and circuits have been developed. Substrate

development, substrate-ink interaction and screen-printing have been carried out in the

first year of the project

Development of Multi Element Focused Ion Beam (ME-FIB)

This part of the proposal is aimed at developing a Focused Ion Beam system

based on a compact microwave driven plasma ion source, which would provide ion

beams of different elements such as Ar, Kr, H2, N2, B etc. The main objective of this

development work is to provide focused ion beams of a variety of elements, which is

currently limited only to Galium as in liquid metal based ion sources. A multi element FIB

would greatly increase the functionality and open flood gates of application. This

research activity is not only first of its kind in India but also in the world. The first attempt

would be to deliver ion beams of inert gases. Such systems have not been developed

yet and are not commercially available. There are a few efforts world wide in this area

which are based upon RF plasmas, and are primarily in the United States. There has

been significant progress in the design and fabrication of ion beams using microwave.

3

Vision & Mission

The national initiative on Nano-Science and Technology has funded an unique interdisciplinary proposal to setup a “Centre for Nanotechnology” at IIT Kanpur, where focused development of technologies based on the rapidly developing nanosceince can be developed. At IIT Kanpur, the Project has been formulated to carry out, in its first phase, technology development in the following three inter-related areas: (i) Development of Printable Organic Electronics with Organic-RFID tags as the first

demonstrator prototype, (ii) Nano and meso-scale patterning based technologies of polymers with applications in

fluidics, sensors and manufacturing of programmable structures, and (iii) Development of a versatile focused ion beam tool based on microwave plasma ion

beam for applications in patterning and templating of soft-materials and substrates. The Project has been initiated in January 2007 with a current outlay of about 12.0 Crores for a period of 5-years. Strategies:

• Active partnership with Industrial partners and user agencies:

Technology development is not possible in isolation from the market or the end-

users. The researchers and faculty need to be constantly in touch with industrial

realities through active partnership with relevant industries. The industries need

to be sensitized to the potential of these emerging technologies. This proposal

strives to bring together user agencies such as Railways, Automotive and

Aerospace industries into active collaboration.

• Product development is focused on those key enabling products which lead to

wide applications basket.

The Center for Nanotechnology at IIT Kanpur will be an internationally recognized Center for development of technologies based on nanoscience and nanoengineering of soft materials such as polymers and molecular solids. The Centre will facilitate conversion of ideas, inventions, and innovations to useful prototypes and applications by providing an interactive technology platform for inventors and users.

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• Enabling formation of synergistic teams of creative individuals and empowering

them with freedom and flexibilities.

• Directed consolidation of a variety of smaller projects in Nanoscience and

Nanoengineering projects.

• Creating centralized facilities for highly interdisciplinary teams to enable them to

contribute at progressively higher levels of value chain in technology

development.

• Managing mission mode projects with sensitivity to academic needs for diversity

and freedom.

Objectives of the Centre: The importance of nanoscience and nanoengineering is widely recognized and there has

been a spurt of research, development and inventions in the area. Focused and

synergistic efforts are needed to complete the chain of innovation by enabling their use

in practical devices and ultimately convert them to technologies. With this in view, this

proposal seeks to set up a Centre for Nanotechnology with the objectives of

a) Providing facilities and systems so as to enable demonstration of prototype

devices using ideas and inventions in nanoscience and technology, and make

the fruits of nanotechnology available to user agencies, and promote industry-

academia interaction with such technologies as the foci;

b) Setting up enabling facilities for nanotechnology based device development with

specific initial focus on printable electronics using soft materials such as

molecular solids and polymers and their heterostructures with inorganic systems;

c) Encouraging researchers in nanotechnology to harness the capabilities in

nanopatterning and structures in soft materials for applications in fluidics,

sensors, and manufacturing;

d) Developing technology tools such as focused Ion Beam as a product and

demonstration of its capabilities in prototyping of devices based on

nanotechnology;

e) Providing an academic platform, leadership, knowledge base and enabling

technologies in the fast changing areas of polymer electronics and

nanoengineering based on continuous fundamental research, innovations, brain-

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storming and networking with industry, research organizations and educational

institutions.

f) Training of graduate students, research associates, post-doctoral fellows and

faculty of other institutes/universities in the emerging areas of nanomaterials,

nanotechnology and polymer based devices, thereby creating an expert base in

our country.

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Organizational Structure, Personnel & Budget Milestones & Deliverables

• The Centre will be formed immediately after sanction is received, and

preparation for the construction of building and purchase of equipment will

commence. During this period, work on different components of the project will

be initiated with the centre acting as a virtual entity. We hope to complete the

construction of building within one and half years and installation of all major

equipment within six months of occupation of the building along with the clean-

room.

• For the proposed Centre, all facilities and equipment will be located under one

roof. This is of special importance since most activities of the centre are centred

around fabrication and processing. Most characterization equipment required in

the process of fabrication will be located in the building.

• During the first one and half year, preliminary technical work would be carried

out in existing Laboratories of the Institute, and sufficient technical progress is

expected to be achieved, while the physical centre is under construction.

Structure and Organization:

About 35 faculty members of the Institute are currently interested in various aspects

of nanotechnology of concern to the Centre. The Centre will have, apart from

involvement of existing faculty members interested in nanotechnology, about 15

scientific and engineering personnel to carry out its activities. We aim to create a

culture that supports a band of highly respected and valued researchers, who are

dedicated entirely to these efforts at the Centre. There will a team of for each project

coordinated by two faculty members.

The success of the Centre would critically depend on our ability to attract motivated

high calibre professionals to join the Centre to work alongside faculty members of the

Institute..

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PERSONAL

Faculty Group

1 Dr. Y.N. Mohapatra Physics

2 Dr. Satyendra Kumar Physics

3 Dr. Baquer Mazhari EE

4 Dr. Deepak Gupta M.M.E

5 Dr. Monica Katiyar M.M.E

6 Dr. S.S.K.Iyer EE

7 Dr. Sidhartha Panda ChE

8 Dr. Ashish Garg MME

9 Dr. V.N. Kulkarni Physics

10 Dr. Sudeep Bhattacharya Physics

11 Dr. Ashutosh Sharma ChE

12 Dr. Animangshu Ghatak ChE

Current Personnel: Research Scholars (Ph.D) - 08 M.Tech Students – 09 B.Tech/ M.Sc. – 04 Project Scientists/Engineers - 3

Hence, we would like to use the flexibilities of appointing visiting and adjunct faculty

from other reputed national and international institutions.

The Centre would endeavour to draw on the complementary expertise of faculty

available through frequent group discussion to solve technical and scientific

problems encountered. It is imperative to find smarter ways of solving problems in

prototype development to be in the reckoning for leadership in the area.

This would need managing Mission Mode in Academics with focus on

• Quality manpower

• Equipment upkeep

• Effective management of experts’ time

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• Partnership with user agencies such as the Railways, Space, DRDO and

Industry

• Creation and commercial exploitation of IPR

It is important to ‘build-in’ sustainability beyond five years in all the above key areas.

We expect involvement of about 50 student projects at levels of B.Tech, M. Tech and

Ph.D at any time when fully operational. Our experience shows that one way of

ensuring a mutually enriching interdisciplinary research environment is to plan Ph.D.

and M.Tech, B.Tech. projects which dovetail into the longer goals of the centre with

joint supervision of thesis by more than one faculty member. Students working at the

centre from different disciplines and departments are the agents for creating such an

interdisciplinary research environment.

In the organizational structure shown in Figure 2.2. We expect the NSTI expert

committee along with other eminent experts in the area to serve as the National

Advisory Committee to the Centre. In addition, there will be an Industrial Interface

Committee guiding the Centre Management Committee on proactive engagement

with industry for collaboration and possible commercialization of IPR generated at

the Centre.

The day-to-day activities of the Centre will be guided by a Core Group of faculty

members and scientists at the Centre. A Centre Management Committee headed by

the Director will hold periodic internal review of the progress. This will be in addition

to the national level review of activities by DST expert committee as per existing

norms.

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10

Significant Achievements : WORK ELEMENTS PRINTABLE ELECTRONICS

A) Initial Phase Micro-projects B) Developing the Blueprint for Printable Electronics

---------------------------------------------------------- Sub-Projects:

I. Circuit & System Design II. Substrate Development, Ink and Surface Interactions

i) Flexible ii) Silicon Based Test Bed

III. Passive Components Development i. Nano Gold ii. Nano Silver impregnated PEDOT iii. Spin Coated Structures as Test

IV. OTFT Development: a) Structure b) Dielectric Multilayers c) Semiconductor & Interfaces d) Embedded Dielectrics

V. Material Development a) Synthesis b) Processing c) Characterization

VI. Printing Process Development a) Screen Printing b) Inkjet Printing c) Gravure & Nanoimprinting

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Nanostructures and Nanomaterials for Printable Electronics 1. Synthesis of soluble SWCNT from shorten SWCNT

SWCNT constitute an important new form of carbon that may find applications in

many field due to its metallic and semi-conducting properties. The functionalization

chemistry of open ends and sidewall of SWCNT is expected to play a vital role in

tailoring the property of nanotubes. All the current known form of SWCNT is insoluble

in organic solvents making it difficult to explore the properties towards the electronic

applications. The SWCNT were dissolved in organic solutions by derivatization with

thionylchloride and octadecylamine(ODA) to the open ends of SWCNT via formation of

amide functionality. The soluble SWCNT were prepared as 200 mg of shorten SWCNT

(as received) were stirred (for oxidation) with the mixture H2SO4 and HNO3 (ratio 1:3)

for 30-45 min and filter and washed with excess of water. 68mg of oxidized SWCNT in

15ml of SOCl2 (with 1ml of dimethylformamide(DMF)) at 70oC for 24hrs. After

centrifugation the brown colored supernatant was decanted and remaining solid was

washed with anhydrous tetrahydrofurane (THF). After centrifugation the pale yellow

colored supernatant was decanted. The remaining solid was dried at room temperature

under vacuum. A mixture of resulting SWCNT and 2g of ODA was heated at 90oC for

4days. After cooling to room temperature, the excess of ODA was removing by washing

OH

OSOCl2, DMF

70oC 48hnCl

O

n

OR

O

n

HNO3+H2SO4(1:3)45min,10min sonication80-130oC RNH2

95oC, 96hrs

Step-I Step-II

Step-III

R=C18H35

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with ethanol four to five times. The remaining was dissolved in dichloromethane (DCM)

and pass with short plug silica-gel column. Black or dark brown color filtrate was

evaporated to dryness. The resulting black solid dried at room temperature under vacuum.

Picture of black solid and unsaturated solution is as shown in the figure 1.

Figure 1 : (A) Unsaturated solution of functionalized SWCNT in dichloromethane (b)

Solid form of funtionalized SWCNT

In the contrast as prepared shorten SWCNT is insoluble in the all the organic

solvent but functionalized SWCNT is soluble in most of organic solvents such as

dichloromethane, Chloroform, toluene, chorobenzene. No precipitate was observed in the

dichloromethane solution after

prolong standing. The FT-IR

spectrum of soluble SWCNT shows

peak at 1672 cm-1, which indicate

amide linkage. Proton nuclear

magnetic resonance (1H NMR

400MHz, CDCl3) of soluble SWCNT

shows peak at δ 0.85(3H, t), 1.23(s,

34H) shows the presence of long

(A) Solid SWCNT (B)

300 400 500 600 700 800 900

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

Abs

& P

L

Wavelength(nm)

SWCNT_DCM_Abs (IodineDoped)

SWCNT_DCM_Abs SWCNT_DCM_PL

13

aliphatic chain. Absorbance of unsaturated solution in DCM is as shown in figure

2, it is featureless up to 300nm. Upon doping with iodine, new band appear at

357nm. Photoluminescence of dichloromethane solution of functionalized

SWCNT was also measured and shown in figure 2. Emission spectra have broad

maxima center at 525nm. The SEM pictures of the reaction product of shorten

SWCNT and ODA is as shown in the figure 3. In SEM image of oxidized SWCNT

bundles of nanotubes are clearly shown.

Figure 3: SEM picures oxidised SWCNT and the ODA funtionalised solid SWCNT

As funtionalised SWCNT is soluble

in organic solvent we tried to make a device

for the conductivity measurements. 24mg/ml

soution of functionalised SWCNT in

dichloromethane was coated on the

precoated PEDOT:PSS substrate

(PEDOT:PSS was coated over ITO coated

glass substare) and was dried at 120oC for

2hrs under high vacuum. An Al electrode

was thermally evaporated over SWCNT

layer at pressure of 10-6 Torr and the active

area of the device was 6mm2 and 8mm2. The

OH

O

n

0 1 2 3 4 5-5.0x10-5

0.05.0x10-5

1.0x10-4

1.5x10-4

2.0x10-4

2.5x10-4

3.0x10-4

3.5x10-4

4.0x10-4

4.5x10-4

5.0x10-4

5.5x10-4

6.0x10-4

6.5x10-4Device Structure : ITO/PEDOT:PSS/SWCNT/Al

Cur

rent

(A)

voltage(V)

Figure 4: I-V characteristic of spin coated SWCNT

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devices were sealed under nitrogen environment. I-V characteristic has been measured as

shown in figure 4. Current is linear upto the 2 volt with the applied voltage.

2. Synthesis of thiol capped Gold nanoparticles

It has been known for some time that metal nanoclusters have reduced melting

and sintering temperatures when compared to their bulk counterparts. Monolayer

protected clusters of gold protected by alkanethiols can be dissolved into common

nonpolar solvents such as toluene, THF, and hexanes, and are therefore suitable for inkjet

and screen printing. Their low sintering temperatures make them potentially suitable for

use in electronics in plastic, since they may potentially be annealed at low temperatures

to form low resistance conductor films. Thiol-derivatized gold nanocluster technology

suitable for use in printed circuits on plastic. We are optimizing the best way of getting

low anneal temperature gold nanocrytals by optimizing the different parameters involved

in the synthesis.

Sysnthesis of gold nanocrystals: 398mg of tetrooctylammonium bromide was mixed with

18ml of toluene and added to 100mg of HAuCl4.xH2O in 25 mL of DI water. AuCl42-

was transferred into the toluene and the aqueous phase was removed. A calculated mole

ratio of an alkanethiol with varying thiol:gold mole ratio was used for different size of

gold nanocluster. Thiols with lengths ranging from 4 carbon atoms to 8 carbon atoms

were used. Sodium borohydride mixed in 25 ml of water was added into the organic

phase with a fast addition over approximately 10 s. The mixture reacted at room

temperature for three and a half hours. Reduced the volume of toluene with a rotary

evaporator and pour into the MeOH and wash repeatedly 2-3 times with excess of

MeOH. Then residue was pour into the vessel with 200-300ml of ethanol and kept for

1. HAuCl4.xH2O(aq.Solution)Tetraoctylammonium bromide (TOAB) ( Solution in Toluene) 2. Alkane thiol(C4, C6, C8)

3. NaBH4

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overnight at –18oC. Filter the black particles suspended in ethanol and dissolved in

toluene.

Absorbance was measured by the Uv-visible spectrophotometer as shown in the figure 5. Two peaks appear at 506nm and 346nm in the 4-carbon chain thiol capped gold nanocluster. To determine the size of nanocrystal dilute solutions of the same were deposited over the carbon coated copper grid of 400mesh size and analysed using high-resolution transmission electron microscope (HRTEM) and it was identified, as the size is less than the 5nm(figure 6).

Thermal gravimetric analysis: Black solid obtained was used for thermal gravimetric

analysis (TGA) and representative TGA curve is shown in the figure 7. The onset

temperature is approximately 200oC. The weight loss for the different thiol:gold ratio

sample was different. For 1:1 it is 20%, 2:1 is 23% and 4:1(32%)

200 400 600 800

0.0

0.3

0.6

0.9

C4(1:1)

C4(4:1)

C4(8:1)C4(16:1)

Nor

naliz

ed a

bs

Wavelength(nm)Figure 5: Absorbance of toluene solution of butanthiol capped gold nanocrystals

Figure 6: HRTEM images of octanethiol capped gold nanocrystals on carbon coated copper grid

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Heat testing: toluene solution

thiol capped nanocrystal was

pipetted and make a film on the

silicon plate and then it was

heated on the hot plate. Upon the

adequate heat, the film converted

to a continuous gold conductor.

This happened through a two

step process, involving the

sublimation of the akanethiol,

followed by the melting, coagulation and immediate solidification of the gold nanocrystal

for form a continues gold films. The thiol burning temperature was identified visually, by

the transition of film color of nanocrystal from black to golden. All the aforesaid results

were summarise in the table.

Alkane thiol C4 C6 C8

Alkane thiol:Gold ratios

16:1, 8:1, 4:1, 2:1, 1:1,

16:1 4:1, 2:1, 1:1, 1:6, 1:12

Size (AFM) 5-10nm 5-10nm 5-10nm

Size (HRTEM) - - < 5nm

Sintering Temperature on Silicon substrate

132-139oC 135-145oC

140-150oC

Absorbance yes yes

IR(before TGA) Yes

IR (after TGA) yes

TGA(%wt loss)

1:1(20%), 2:1(23%), 4:1(32%)

0 50 100 150 200 250 300 350

4500

5000

5500

6000

6500

7000

Temperature

TG(m

icro

gram

)

-100

0

100

200

300

400

500

DTG

(microgram

/min)

Figure 7: Representative curve of TGA of octantane thiol capped gold nanocrystal

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3. Development of soluble Metal Nanoparticles in PEDOT & PMMA

Loading of nanoparticles in polymers are being developed both for conducting and

dielectric applications. Aqueous solutions of silve nanoparticles and PEDOT has given

one order of magnitude increase in conductivity and the parameters of fabrication are

beign oprimized in an M.Tech Project.

Silver nanoparticles are also being put into PMMA to increase the dielectric constant and

decrease . This optimization is being carried out

OTFT Development: Structure & Interfaces

One of the important components of the organic electronics is organic thin film

transistor (OTFT), which have been proposed for applications such as display drivers, radio-frequency identification (RFID) tags and sensors. Our group has been focusing on

OTFT development. Although, OTFT technology has made significant progress in the

recent past in achieving high mobilities, it still faces a number of challenges at the

fabrication, materials and device physics level. These include limited understanding of the

effect of organic semiconductor structure on carrier mobility, charge injection from metal,

and charge transport at the dielectric/semiconductor interface. A concentrated effort is

made to analyze the effect of each of these issues separately on the device performance

through experiments, analytical models and numerical simulations. Our methodology is to

numerically simulate the experimentally obtained OTFT device characteristics: (i) to

estimate bulk and interface trap types and concentrations in the organic semiconductor; (ii)

to highlight the effect of contacts through two different design of OTFTs i.e. top (metal is

deposited above the organic semiconductor) and bottom (metal is deposited prior to the

organic semiconductor) contact OTFTs; and (iii) to investigate the effect of

dielectric/semiconductor interface structure on device characteristics for different

semiconductor thicknesses. We used pentacene as the organic semiconductor, which has

demonstrated consistent high mobility in OTFT devices. Numerical simulations are done

on a commercially available software ATLAS (Silvaco), originally developed for inorganic

semiconductors. (This work is part of Ph.D. thesis of Dr. Dipti Gupta, 2008, IIT Kanpur)

Among the available organic semiconducting compounds pentacene has the highest

mobility (1.5 cm2V-1.s-1). Therefore, scope of another project was to optimize the deposition

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parameters of OTFT. The parameters considered were pentacene deposition rate,

substrate temperature, gold deposition rate and gold thickness. Pentacene deposition rate

was varied from 0.5-2.0 nm min-1 at 70oC substrate temperature. Mobility improves by

increasing the deposition rate of pentacene from 0.5 -2.0 nm min-1. Under optimized

deposition condition pentacene films show closely packed grains, dominance of thin film

phase and increase in crystallinity. At 2.0 nm min-1, substrate temperature was varied from

50-70oC. Mobility improves by reducing the substrate temperature to 60oC. This is

concomitant with changes in morphology. Analysis of AFM image shows higher density of

grains with dendritic structure. OTFTs were also fabricated with Au deposition rate 1.0 and

5.5 nm min-1, Au deposition rate had no effect on OTFT characteristics. But when Au

thickness was increased (Au deposition time increased), pentacene mobility is adversely

affected. (The details can be found in M.Tech. thesis of I.V. Kameshwar Rao, 2007, IIT

Kanpur)

4. P3HT TFT with PMMA as gate dielectric

TFT Fabrication: A schematic cross section of the TFT fabricated is shown in Figure 1. A PMMA solution of 75mg/cc concentration in n-bultaylaccatate was spin coated for 550nm thickness. A P3HT solution of 25mg/cc concentration in chloroform as spin speed was 2000rpm at 60 seconds the thickness was measured 200nm. This was followed by annealing to remove the solvent from the P3HT and PMMA with each step. Rapid evaporation of the solvent is essential in this process. The source/drain contacts on top of the P3HT layer were formed by thermal deposition of Au through a shadow mask. The channel length and width for these devices were 60 μm and 1000 μm respectively.

TFT Characterisation and Results: Kethley’s 4200-SCS Semiconductor Characterization System was used to measure I-V characteristics of the devices. The ID-VG curve (Figure2) shows good gate control with an ION/IOFF ratio of ~102. The threshold voltage was determined to be -12 V. Saturation field mobility near 0.09 cm2 V-1 s-1. Sub-threshold slope of about 9V/decade at Vgs = -25V. From the sub-threshold swing, the interface state density was calculated to be 3.6×1012 cm-2 V-1 s-1. Output characteristics of P3HT transistor shown in figure 3. The drain bias was swept from 0 to -35. Data are presented for 60µm channel length. The channel width is 1 mm.

FIG-1 P3HT TFT with PMMA as gate dielectric

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0 -10 -20 -30 -40

0.0

-0.1

-0.2

Vg=-15V Vg=-20V Vg=-25V Vg=-30V Vg=0V Vg=-5V

Id(u

A)

Vds(V)

Dielectric layers with PMMA were optimised for leakage and thickness although leakage is high in these devices. In the P3HT-PMMA devices, the on-off ratio is poor and the threshold voltage is -12 V. The results are encouraging from the point of view of achieving all organic transistors in the future for various high volume and printable electronics applications.

FIG-3 ID Vs VG and IG Vs VG

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5. Multiple Polymer with AVPV and CN-AVPV (Y N Mohapatra, C K Suman, Awnish, Durgesh Triapthi, Dhirendra Sinha) Printable Electronics requires multiple layers to be deposited from solution. Spin-casting of such layers are being developed to study the quality of interface using impedance spectroscopy.

NOC8H17

C8H17O

C8H17

NOC8H17

C8H17O

C8H17

C8H17 C8H17

N

C8H17

n

AVPV

CN-AVPV

NC

CN

The mixing of layers at the interface has shown to have beneficial effects on the properties of the device. 6. Simulation of Dynamic Characterisitics of Organic TFT and Diodes: (Dheeraj Mohata, Paritosh Manurakr, D.Tripathi, Y.N. Mohapatra, SSK Iyer ) The ATLAS platform has been used extensively to model multi-layer structures of diodes and TFT structures to study the impact of injection, accumulation and trapping of carriers in these structures on capacitance-voltage, impedance and frequency dependent conductance characteristics. The effect multilayer gate structures and a variety of interface distributions in OTFT has been studied in detail as parts of two M.Tech Teheses. 7. Development of Screen Printing for Conductive Lines: (Ashsih Garg, SSK Iyer and Group) A home made screen printing apparatus has been developed and optimization of parameters for printing conductive silver lines have been carried out. This will be a major contributor to making cheap printing of large sized conductive lines in printable circuits.

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Fig: The silver lines on screen and printed on plastic substrate. 8. Substrate Development, Substrate Ink Interaction: (Satyendra Kumar, Vandana Singh, Siddharth Panda) Most printable electronics require high quality conductive ITO to be deposited on plastic substrates through low temperature deposition processes. Good quality ITO with following characteristics has been successfully deposited through RF sputtering and the quality is better than commercially available. Transmission: 75% as Mylar plastic has only 85% of transmission in the visible range.

1. Sheet resistance ~ 15Ω/square and for commercially available substrates ~30 Ω/square

2. Work Function: 4.6 eV comparable to commercially available ITO coated substrates

3. Surface roughness: 1.32 nm The large scale fabrication has not been attempted,a nd we are currently dependent on outside sources for these substrates. In this context, we will be looking at spreading and penetration of ink by studying the interfacial energies (from contact angle measurements), the effect of ink properties (e.g. viscosity) and surface texture. We also will be looking at the simultaneous conductive and adhesive options and the parameters controlling the degradation of the lines. Initial studies on texturing on silicon substrates have been carried out. 9. Printable Circuit and Antenna Design: (A.R. Harish, Anurag Sindhu, Arjit Ashok, Siddhartha Omar, Sumit Veerawal ) Demonstration of use of polymer electronics for making an RFID tag operating at 125 kHz was attempted with the following steps:

• Design a simple circuit to demonstrate one bit transponder. • Simulate the circuit. • Implement the circuit on breadboard using discrete circuit elements. • Design a simple circular spiral planar antenna.

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• Implement the circuit on a general purpose PCB. • Finally implement the circuit using polymer semiconductor. • Study the relation between voltage induced and the separation between the reader

and the tag antenna using the breadboard implementation of the circuit.

The reader antenna circuit is basically a series LRC circuit. The series circuit is chosen to maximize current through the reader, so that transmitted power is maximized. The tag circuit consists of an inductor in parallel with the capacitor. A parallel circuit is chosen for the tag to maximize voltage throughout the system. The tag is tuned to the resonant frequency such that the voltage induced in the tag is maximized. The tag circuit also has a half-wave rectifier, which converts the received signal into a d.c. voltage. This RFID system works on the principle of amplitude modulation. The reader can switch between two voltage levels. The tag circuit has a comparator sub-circuit, which demodulates the signal and indicates the output by glowing the corresponding LEDs.

Fig. The circuit for simulated and fabrication The breadboard implementation was carried out at WL 212. Circular planar coils made of laminated copper coils were used as inductors. Radius of coils = 2.75 cm Number of turns of coil = 23 Voltage Applied = 10V Operating Frequency = 125.2 KHz Separation between the Reader and the Tag = 10 mm Voltage across Reader antenna = 6 V Rectified Voltage induced in Tag = 6 V We decided to use gold evaporation technique for the fabrication of the antenna. This technique requires a re-usable mask through which gold is evaporated and is deposited on the substrate. But due to the small thickness of the inductor wire required, our attempts to fabricate the mask failed. The thickness of the inductor wire could not be increased beyond 0.25 mm, because that would have required a trade-off with some other

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parameters like inductance, tuning capacitance, operating frequency or the size of the tag. So we concluded that this inductor should be fabricated using some other technique, preferably a printing method. Suggested Future Work:

• Implementation of the tag using polymer semiconductors. • To fabricate the antenna using screen printing and gold evaporation techniques. • Study the relation between voltage induced and the separation between the reader

and the tag antenna for various antennas. 10. Fabrication of Nano-electrodes using FIB for Organic Electronics (Zainul Abadeen, V N Kulkarni, Y N Mohapatra)

Focused Ion Beam (FIB) provides unique capabilities to fabricate nanostructure based devices. Fabrication of metal contact with separation in nanometer and micrometer regime is an integral part of most fabrication tasks in this direction. In this thesis we optimize parameters and procedures to fabricate nanometer to micrometer inerdigitated electrodes using patterning capabilities of FIB on gold and aluminum thin films.

In this sub-project the possibility of fabrication of organic thin film based devices using nano and micrometer interdigitated electrodes using Focused Ion Beam. The difficulties in fabricating nanometer and micrometer separated electrodes using FIB have been studied. Such electrodes have been successfully fabricated using gold and aluminium thin films. The I-V charavteristics of devices fabricated by depositing organic layers such as Alq3 and pentcene have been studied. The efforts are aimed at eventually developing organic thin film transistors with small channel length using these techniques.

Aluminum electrodes with separate of 16nm and and 31nm have been fabricated, and Alq3 has been deposited on them using high vacuum deposition. These devices are compared with electrode separation of hundreds of nanaometer fabricated using maskless lithograpy.On the basis of both Voltage and distance dependence, the current is proved to be space charge related current in these devices, though the corresponding mobility in nanometric channels seems to be much less than that expected in the bulk.

The fabrication of gold interdigitated electorodes is found to be easier than that of aluminium. To test the efficacy of gold interdigitated electrodes, pentacene as a hole transporting layer has been used. Channel length in nanometer and micrometer range have been fabricated from gold thin films using FIB. For nanaometric size devices, the observed I-V characteristics with pentacene is piecewise-linear showing the evidence of ohmic and defect related space charge conduction. The devices with a separation of 1μm, however, shows space charge limited current with a square dependence on voltage. Devices with a separation of 2μm showed a voltage exponent between 3 and 4, which is normally observed for field enhanced mobility in these materials. We conclude that the quality of material and the conduction paths in nanometer sized channel lengths is different from those grown between micrometer separated electrodes.

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11. Status of development of the ME-FIB (S. Bhattacharjee, Department of Physics, IIT Kanpur)

The project on the development of the Multi elemental focused ion beam system (ME-FIB) has made significant progress. The project has provided opportunities for several M .Sc projects and two Ph.D students are currently involved in the research and development undertaken so far. Significant journal publications have already resulted from the efforts, which are creditable and indicate a remarkable achievement during the time since the inception of the project. Since it is a first time development, several aspects of the ME-FIB have to be first researched and then developed for incorporation into the device.

The development of the multielemental focused ion beam system has been approached using a microwave driven plasma source in different steps. In parallel to the several experimental works being carried out, the theoretical background and physical principles on which the source is based are being developed and investigated to provide a better understanding of the subject and operation of the ion source. Recently the subnanosecond electron transport in polarized electromagnetic waves leading to an understanding of the prebreakdown phase of the gas under the given ion source geometry has been researched and the results recently published [1]. Classically, it is well known that the number of collisions N suffered by an electron in diffusing out of the plasma ion source is given by N ~ (Λ/λ)2, where Λ is the characteristic diffusion length and λ is the mean free path. For the first time, the electron random walk has been clarified in the presence of polarized electromagnetic waves and it is found that in the presence of the field, the variation of N gets modified as N=A(Λ/λ) + B(Λ/λ)2. These results dictate the electron energy gain and have important implications in early gaseous breakdown in the ion source thereby deciding the microwave power, frequency etc. The results are summarized in Fig. 1.

Figure 1. (a) Shows the number of collisions suffered by an electron N versus Λ/λ in the field free case. The square law is clearly reproduced. (b) Variation of N in the presence of the electric field. u is the average energy gained per electron per collision.

(a) (b)

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We have then investigated the phenomena of quasisteady state generation in

interpulse plasmas – which is a new regime of plasmas between pulses of high power microwaves and will be important during pulsed operation and heating of plasmas in the ion source [2]. The quasi steady regime has been discovered by us earlier. It has been found that the application of high power microwaves (~ 100 kW peak power) in short duration pulses (~ 1 μs) leads to development of quasi steady state plasmas in the interpulse regime as shown in Fig 2 (a) where the microwave power does not exist. The variation of the plasma flat top time with discharge pressure and power is shown in Figure 2 (b) and (c) respectively. The technique of pulsed heating provides us a totally new outlook particularly for generating pulsed ion beams for several applications.

Figure 2. (a) Generation of plasma quasi steady state. Note the high power pulses of 1.2 μs pulse duration and (b) Variation of the flat top duration τflat with discharge pressure and (c) with microwave power Po.

In the experimental side, as a first major step, the ion source part has been

developed which employs a nonconventional multicusp plasma ion source with a subcutoff dimension. In order to optimize the source properties, some basic studies on the plasma source like studying the plasma parameters, the effect of different multicusp configurations like Hexapole versus Octupole, effect of the size of the multicusp for

(a) (b)

(c)

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making the source compact, finding the optimum pressure and microwave power levels of operation etc have been already accomplished and the results recently accepted for publication [3]. We have also studied the radial and axial plasma uniformity in the source which is important for deciding the geometry and location of the ion extraction electrodes, particularly the plasma electrode. The study of the plasma parameters indicate that the octupole multicusp configuration provides better plasma confinement and plasma heating, which makes it more efficient than the hexapole geometry. These results are shown in Fig. 3.

Figure 3. (a) Variation of the plasma density with radius of the ion source for the hexapole and octupole multicusp configurations. The variation of the static B field for the two cases is also shown. (b) Axial variation of the plasma density for the two configurations. The cross indicates the optimum location of the plasma electrode for extracting the ions and (c) variation of the plasma density and electron temperature with discharge pressure.

Secondly, we have been looking at the ion beam extraction part. The total

extractable ion current is measured using a Faraday cup. The initial experimental set-up is shown in Fig. 4. Gas species such as Argon, Krypton, Hydrogen etc has been used for generating multielemental ion beams for both multiple beams and single focused beams. The total ion current densities ranging from a few hundred to over 1000 mA/cm2 have been obtained for different plasma electrode apertures at different pressures and

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microwave powers [3]. Approximate beam brightness calculations indicate that close to commercial Liquid metal ion source (LMIS) value is possible in the present system. We have found that for increasing the microwave power density in order to achieve high plasma density and electron temperatures, the plasma source can be made compact by overcoming the waveguide geometrical cutoff limitation [4] and the ordinary mode (O-mode) plasma density cutoff. We have established the physical mechanisms for plasma generation and sustenance in this compact subcutoff plasma source, which are the keypoints for the excellent operation of the ion source. This research has been recently published in Applied Physics Letters [5]. The optimum operating conditions for beam extraction have also been obtained.

Figure 4. (a) Schematic of the experimental apparatus: (MW) microwaves, (WG) rectangular waveguide, (W) quartz window, (VC) vacuum chamber, (MC) Multicusp, (PE) plasma electrode, (FC) faraday cup, (A) ammeter, (HV) high voltage power supply (b) Poisson simulation of multicusp magnetic field (octupole).

Figures 5 and 6 shows the current densities of the extracted ion beams as a function of microwave power, extraction potential, plasma electrode aperture size and for different gas species such as Krypton, Argon and Hydrogen. The optimum pressure of operation is found to be around 2×10-4 Torr since Ji has a maximum value at this pressure. The behaviour at 9.5×10-5 Torr is possibly due to a mode change leading to a change in plasma density. In Fig. 6(b), Ji for three gas species viz Krypton, Argon and Hydrogen are compared at 2.5×10-4 Torr, the microwave power is 270 W and the plasma electrode has a 5 mm aperture size. As predicted, Ji shows an inverse relationship with ion mass. In both the cases we find that the extracted ion current is far from saturation at -5 kV. The variation of Ji with microwave power is shown in Fig. 5(a) with extraction potential kept at -4 kV and the PE aperture of 5 mm. The operating pressure is 2.5 × 10-4

Torr. Ji tends to increase with microwave power. The increase in Ji is more prominent for lighter gas atoms. Fig. 5 (b) shows the dependence of Ji on plasma electrode aperture size at 270 W microwave power. At -5 kV, Ji is a maximum for 1 mm aperture (~ 6230 mA/cm2) which is promising for focused ion beam system. Recently plasma ion sources have been found to have high angular intensity (dI/dΩ) which make them more suitable for large volume milling in FIB applications as compared to commercial LMIS which fails at higher beam currents (> 10 nA) [6].

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After optimizing the plasma ion source and measuring the total ion current density, we are currently starting to investigate the focused ion beam current and spot size. The AXCEL-INP code is being used for simulating the focusing of ion beam using a set of two electrostatic Einzel lenses consisting of three electrodes each. The first lens makes the beam parallel and the second one focuses it to a spot size.

Figure 5 Figure 6

F Figure 5. (a) Extracted ion current density, Ji as a function of microwave power for three gas species viz krypton, argon and hydrogen (b) extraction potential, V for three aperture sizes of 1mm, 5mm and 8mm. Figure 6. Extracted ion current density, Ji as a function of extraction potential, V (a) at different pressures and (b) for three different gases.

We have also employed a 500 micron slit in the path of the beam. The parallel beam from the first lens is reduced in size by the slit and the out coming beam is focused using the second lens to < 10 μm spot size. Another beam limiting aperture and or the focusing field profile of the second lens may be modified to further reduce the spot size. Currently ongoing efforts are to get the smallest possible beam spot size, however this may be considered as a reasonable starting point. One set of Einzel lenses has already been designed as per the code and we are currently implementing this in the system. New experiments are being planned to determine the ion energy distribution function (IEDF) using a retarding field analyzer developed in our laboratory and to study the obtained spot size and the correlation between them. Figure 7 shows a typical example of the plasma

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(ion) energy distribution for ME-FIB, a comparison is made with an inductively coupled plasma (ICP) for FIB applications being developed by Boswell’s group at the Australian National University is shown in Fig. 7(b). In LMIS the spread in the ion energy distribution is about 5 eV. Figure 7. (a) Ion energy distribution at a pressure of 2.5x10-4 Torr and 300 W of microwave power. (b) An example of the ion energy distribution by Rod Boswell’s group for an inductively coupled plasma for FIB applications.

Figure 8: Ion beam trajectory plot, with a two Einzel lenses in the beam path using AXCEL-INP code. There is a beam limiting aperture of 500 micron aperture size after the first lens.

0 20 40 60 80 100

0

100

200

300

400

Retarding Voltage (V)

Col

lect

or C

urre

nt (n

A)

0100200300400500600

dI/dV (a.u.)

ΔEFWHM = 6.1 eV

(a) (b)

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The initial simulation results of the focused ion beam using the AXCEL-INP

simulation code is shown in Fig. 8. One set of Einzel lenses has been designed as per the code and we have installed this in the system. The plasma chamber and the focusing column are separated and differential pumping is used for effective beam transport. We designed a probe for measuring the focused beam current and beam spot size. The focused beam current measurements have been carried out for extraction potentials until 10 kV and also the focal point of the beam has been found. Currently we are working on determining the beam spot size and optimum beam transport. Future plans include the accurate determination of beam spot size, the use of double Einzel lens for sub micron focusing etc. References including publications from the work carried out so far: [1] Indranuj Dey, Jose V. Mathew, Sudeep Bhattacharjee and Sachin Jain, "Sub-nanosecond electron transport in a gas in the presence of polarized electromagnetic waves", Journal of Applied Physics 103, 083305 (2008) . [2] Sudeep Bhattacharjee, Indranuj Dey, Abhijit Sen, Hiroshi Amemiya, "Quasi steady state interpulse plasmas", Journal of Applied Physics, 101, 113311 (2007) [3] Jose V. Mathew, Abhishek Chowdhury, and Sudeep Bhattacharjee, "Subcutoff microwave driven plasma ion sources for multi elemental focused ion beam systems", accepted for publication in Review of Scientific Instruments (May 2008). [4] S. Bhattacharjee and H. Amemiya, "Production of microwave plasma in narrow cros-sectional tubes; effect of the shape of cross section", Review of Scientific Instruments, 80, 3332 - 3337 (1999). [5] Jose V. Mathew, Indranuj Dey, Sudeep Bhattacharjee, "Microwave guiding and intense plasma generation at sub-cutoff dimensions for focused ion beams", Applied Physics Letters, 91, 041503 (2007) [6] N.S. Smith, D.E. Kinion, P.P. Tesch and R.W. Boswell, Microsc Microanal 13 (Suppl 2), 180 (2007).

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Financial Status: BUILDING & CLEANROOM: Sl No.

Head

Allocations (Rs. In Lakhs)

01 Building 75.00

02 Cleanroom and accessories 75.00

EQUIPMENT: Sl No.

Head

Allocations (Rs. In Lakhs)

01 FIB Technology

300.00

Organic Electronics

a) Integrated JetLab Print Platform with Interroferrometric Stage (Micro Fab Technologies Inc.)

b) Nanolithography and Manipulation Scanning Probe Microscope System with Monitors including accessories for vacuum holding of samples

c) Materials Printer with heated paltedn, drop visualization, and fiducail camera,Swith 20 Materials Cartridges (16 nozzle, 10picolitre)

d) Scanning Electron Microscope for Nanomanipulator Installation (Qunta Inspect FP 2017/11

e) Zyvex Nanomanipulator with Keithley Accessories for Electrical Measurements and Switching

f) Precision Impedance Analyzer (Agilent 4294A and accessories)

g) Function/Arbitrary Waveform Generator Agilent 33250A, 80MHz

h) Semiconductor Parameter Analyzer HP 4155C

i) 330MHz Pulse Pattern Generator Agilent 81110A, & 81112A-FG

j) Infinium 4 Channel Digital Storage Oscilloscope Agilent DSO8104A

k) LCR Meter (20Hz-1MHz) Agilent 4284A and accessories including Kelvin Leads and Tweezers

l) Development of Stamping & Gravure Printing

02

m) Miscellaneous small equipment for developmental platforms

500.00

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FUNDS SANCTIONED: Funds Break Up/Budget Head

Total (Rs. In Lakh)

1st Year (Rs. In Lakh)

2n d Year (Rs. In Lakh)

3rd Year (Rs. In Lakh)

4th Year (Rs. In Lakh)

5th Year (Rs. In Lakh)

Equipment 800.00 760.00 5.00 28.00 4.00 3.00Salary 60.00 12.00 12.00 12.00 12.00 12.00

Contingency 10.00 2.00 2.00 2.00 2.00 2.00Honorarium

Consumables 150.00 30.00 30.00 30.00 30.00 30.00Travel 5.00 1.00 1.00 1.00 1.00 1.00

Clean Room etc 150.00 150.00 0.00 0.00 0.00 0.00Overhead 5.00 1.00 1.00 1.00 1.00 1.00

Total 1180.00 956.00 51.00 74.00 50.00 49.00 Funds Utilized : Approximately Rs. 180 lakhs (as on May 10, 2008) Future Activities and Major Concerns: The printable part of the flagship project is about one year behind schedule in terms of facility development. SPACE:

• The major challenge at the moment is the site prepare the space (including clean room) so that the site is ready for receiving the major equipment.

• Basic Planning of space currently being allocated jointly with Microstructure

Process Group has been carried the details of space sharing of space have been worked out. An implementation plan is on the anvil.

• Once the space is allocated , within a month the Chemistry Laboratories and

Non-clean Room Facilities to be set –up in a war footing.

PEOPLE:

• Major hiring of personnel at the level PDF and scientists can be carried out once the space is made suitable for occupation.

• Currently the project does not budget for support staff. We hope to be sanctioned

a skeletal support staff for the new space and the Centre.

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FACILITIES:

• Some of the major facilities such as the large Ink-Jet printing platform will need foreign travel to get the instrument designed to our needs.

• Most of the facilities’ being planned are processing equipment, and need

specifications to be arrived at keeping in the product in mind. The product specifications have not been frozen and will require intensive discussion and experimentation over next six months.

• An elementary ink-jet printing system is being ordered in the meanwhile for

carrying out initial experiments as originally planned. ACTIVITIES:

• Currently, the groups meet once in a week to plan the activities. This will be made intensive this summer for establishment of the facilities and site planning.

• As in the last year, the Centre would organize fortnightly seminars from experts

• The procedure of becoming a fully fledged Centre will be completed within this

year.

• Once the basic printing facilities are established, more projects apart from the flagship project will be included in the charter of activities of the Centre.

CONCLUDING REMARKS : There is an urgent need to give a concrete shape to the Centre retaining its organic link

with SCDT and Ion Beam Centre. This year will be crucial in terms of both facility

development and firming up the operational and organizational aspects. The interlink

between various subgroups need be developed further for proper product development

orientation.