Introduction

…………………………..

Conclusions

Acknowledgements

Soaking To Sunning: Preliminary Conditions Of Seed Layers For Zinc-Oxide Nanorod Manufacture

Charles Caloia*, Jong Hyun Shim, & Junghyun Cho NSF Research Experience For Undergraduates Poster Session: July 31st, 2015

Department of Mechanical Engineering & Materials Science and Engineering ProgramState University of New York (SUNY) at Binghamton, Binghamton, NY 13902-6000

*-St. Francis College 180 Remsen Street Brooklyn Heights, NY 11201

References1. Yoshimura, M.; Byrappa, K. Hydrothermal Processing Of Materials: Past, Present And Future. J Mater Sci 2007,

43, 2085-2103.

2. Kim, Dong-Ho et al. 'Thickness Dependence Of Electrical Properties Of ITO Film Deposited On A Plastic Substrate

By RF Magnetron Sputtering'. Applied Surface Science 253.2 (2006): 409-411. Web. 28 July 2015.

3. Wirunmongkol, Thanakorn, Narongchai O-Charoen, and Sorapong Pavasupree. 'Simple Hydrothermal Preparation

Of Zinc Oxide Powders Using Thai Autoclave Unit'. Energy Procedia 34 (2013): 810-807. Web. 28 July 2015.

Experiment

Optical MicroscopyKey: SL=Seed-Layer, HTP=High-Temp Prep, LTP=Low-Temp Prep, Hyd=Hydrothermal Prep (45min)

This procedure looks into the conditions of a film substrate used for the production of photovoltaic Zinc Oxide (ZnO) nanorods. With a wide bandgap of 3.37 eV and high excited-state energy of 60meV, ZnO makes for a prime material in electronics such as solar cells and smoke detectors.1 In addition, to allow more ductility, Indium-Tin-Oxide (ITO) films have become prominent substrates with electrical properties, such as a high resistivity bearing a high dependence on crystallinity as observed on glass slides.2 This procedure covers the effects of hydrothermal crystal formation on ITO film via ZnO nanorod growth.

- Several slides implemented had compromised ITO films: finer scratches from human error, but more prominently heat-induced cracks and fissures.

- Even with careful cleaning immediately after Hydrothermal Prep, large ZnO crystals from the Precursor remained on samples, more prominently on the 20mM-treated slides compared to the other 16. There was also a prominent quantity of defects in the glass itself

- Though they still retained similar residue to the 20mM Hydrothermal slides, the 10mM Hydrothermal samples overall retained less damage to the ITO film.

- The slides without Hydrothermal Prep usually encountered the least defects, most likely due to the film’s lack of contact with larger Zinc substrates encountered by the other slides.

- Other than varying regions of damage, the ITO film was mostly preserved, allowing for nanorod growth to be observed under SEM microscopy, per Fig. 1 & 2. Much like this figure, ZnO nanorods formed in optimal conditions bear a hexagonal-prism shape allowing for the best photocatalytic product.3

This project focuses on the ITO film’s integrity: the foundation for the photocatalytic ZnO nanorod film to be manufactured. With factors ranging from the material’s handling to its hydrothermal cultivation, ITO and similar substrate films are fickle media that must be handled quite specifically. Jong Hyun Shim, a grad-student colleague of this preparer, recently noticed an optimal cooling condition for the Precursor that allows for little Zinc residue to form in Hydrothermal Prep involving ice baths. Therefore, the heat of preparation ensures the film’s quality in the detailed processes aforementioned.

This work was supported by the Research Experiences for Undergraduates (REU) Program of the National Science Foundation under Award Number 1263004. Special thanks are attributed to the Mechanical Engineering and Chemistry Departments of SUNY at Binghamton.

24 ITO-treated slides were utilized in varying forms of the above preparation procedures. These slides were separated into two groups of 12 with different Seed-Layer Concentrations: 750mM and 1000mM. Within each of these 12, four groups of three slides were prepared differently on hot plates: two for high-temperature prep (45min & 90min) and the other two for low-temperature prep (2.5hr & 5hr). Two individual slides from each group were then placed in Hydrothermal Prep for 45 minutes: one in a 20mM precursor solution and the other at 10mM; the third of these groups was omitted from Hydrothermal Prep.

Figure 3: The above diagram details the entire process utilized for each slide. 8 of the 24 sample slides have foregone Hydrothermal Prep.

Materials/Approach

Pre-Prep CleaningITO-treated glass slides were first cleaned via Acetone swabbing, 30 minute ultrasonic bathing in 2-Propanol and Deionized Water, and low-pressure (~300 mTorr) Oxygen Plasma treatment.

Seed-Layer PrepVarious concentrations of Zinc Acetate and Monoethanolamine were combined per 10 mL of 2-Methoxyethanol, creating a Seed-Layer Solution. From there, the slides were spin-coated (~500RPM for 9s & ~7000RPM for 30s), then heated at varying times and temperatures; high temperature prep was conducted at 300°C while low temperature prep was conducted at 138°C.

Hydrothermal PrepA “Precursor” solution was then prepared with Deionized Water, Zinc Acetate, and Hexamethylenetetramine (HMTA) and refrigerated to ~5°C. Some slides were placed in Teflon containers to be immersed in the solution; the containers themselves were placed in a ~90°C Silicone Oil Bath for 45 minutes.

ITO Glass 2-Propanol/Water

30min Ultra-Sonic Bath

O2 Plasma treatment

5 min

Spin-Coating/Hot Plate Seed-Layer Prep

High Temp: 300°C for 45min, 90minLow Temp: 138°C for 2.5hr, 5hr

Hydrothermal Prep

45min in 90°C Silicon Bath

24 ITO Slides

12 750mM Seed Layer

3 45min High Temp

Prep3 90min

High Temp Prep

3 2.5hr Low Temp Prep

3 5h Low Temp Prep

12 1000mM Seed Layer

3 45min High Temp

Prep3 90min

High Temp Prep

3 2.5hr Low Temp Prep

3 5h Low Temp Prep

Figure 4: This diagram details the preparation of all 24 slides. Of the rightmost tier, each of the three slides was placed under different Hydrothermal Prep conditions: one with a 20mM Precursor Solution, another at 10mM, and one omitted from Hydrothermal Prep.

Slide Sample Grouping & Measurements

Solution 750mM 1000mM

Seed Layer(per 10mL of 2-

Methoxyethanol)

0.4527mL of Monoethandiamine,

1.646mg of Zinc Acetate

0.6036mL of Monoethandiamine,

2.195mg of Zinc Acetate

Solution 10mM 20mM

Precursor(per 800mL of

Deionized Water)

1.122mg of HMTA,

1.756mg of Zinc Acetate

2.244mg of HMTA,

3.512mg of Zinc Acetate

Figures 1 & 2 : ZnO nanorod growths on ITO-treated glass. (300°C 750mM Seed-Layer Prep)

Swabbed w/ Acetone

Figures 5-12: Eight sample slides. Each represent a trend elaborated in further discussion

Results & Discussion

Figures 13 & 14: The two tables detail the assembly of the two solutions used predominantly in the procedures

Slide A:750mM SL45min HTP20mM Hyd1000x Mag

Slide N:1000mM SL45min HTP20mM Hyd200x Mag

Slide B:750mM SL45min HTP10mM Hyd500x Mag

Slide Q:1000mM SL90min HTP10mM Hyd1000x Mag

Slide T:1000mM SL2.5hr LTP10mM Hyd500x Mag

Slide G:750mM SL2.5hr LTP20mM Hyd500x Mag

Slide L:750mM SL5hr LTPNo Hyd500x Mag

Slide V:1000mM SL5hr LTP20mM Hyd500x Mag