Auger Electron Spectroscopy of In2O on GaAs(001)-(2x4)

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

0 200 400 600 800 1000 1200

Electron Energy (eV)

Au

ge

r S

ign

al (

a.u

.)

As, Ga In

O

Ga As

In:O = 2:1

In2O3(s)In2O(g)+O2(g)

Scanning Tunneling Microscopy and Spectroscopy of Gallium Oxide and Indium Oxide Deposition on GaAs(001)-(2x4)Scanning Tunneling Microscopy and Spectroscopy of Gallium Oxide and Indium Oxide Deposition on GaAs(001)-(2x4)  

Clean GaAs(001)-(2x4) Surface

Clean STM Image Clean Ball & Stick Diagram

16Å16Å

In2O on GaAs(001)-(2x4) 410°C Dose/Low Coverage

0 50Å

In2O Bonding in the Trough Ball and Stick Diagram

Line Spacing of In2O Vs. Ga2O at Monolayer Coverage

0

10

20

30

40

50

60

70

80

90

8 10 12 14 16 18 20 22 >24

In2O

Ga2O

Row Spacing (Å)

Per

cent

age

of S

paci

ng

Approximation of the Density of States for Both Clean and O Adsorbed GaAs(001)-(2x4)

-10.5

23.5

56.5

8

-1.5 -1.3 -1.0 -0.8 -0.5 -0.3 -0.1 0.2 0.4 0.7 0.9 1.1 1.4 1.6 1.9 2.1 2.3

2

3

4

5

6

7

8

-2.0

-1.8

-1.5

-1.3

-1.1

-0.9

-0.6

-0.4

-0.2

0.1

0.3

0.5

0.7

1.0

1.2

1.4

1.7

1.9

2.1

2.3

0

Fermi Level

-0.75

-1.5

Clean GaAs(001)-(2x4)Unpinned

After O AdsorptionPinned

Sample Bias (eV)

dI/d

V/(

I/V

) (

a.u.

)dI

/dV

/(I/

V)

(a.

u.)

1.5eV

0.75eV

Approximation of the Density of States for Ga2Oon Both n- and p-type GaAs(001)-(2x4)

2

3

4

5

6

7

8

9

10

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0

-1

1

3

5

7

9

-1.2 -0.9 -0.6 -0.3 0.0 0.3 0.6 0.9 1.2 1.5 1.8

Sample Bias (eV)

Fermi Level

dI/d

V/(

I/V

) (

a.u.

)dI

/dV

/(I/

V)

(a.

u.)

n-type Ga2O/GaAs

p-type Ga2O/GaAs

Fermi Level

VB

VB

CB

CB

3

-2.0

Electronic Measurements of In2O on GaAs(001)-(2x4)

0

-3.2 -1.0 1.2 3.4 5.6

Fermi Level

0-1.4Sample Bias (V)

In2O on n-type GaAs(001)-(2x4)

0

-0.70

Clean p-type GaAs(001)-(2x4)

Fermi Level

-0.3 1.2

0

-1.5 0

In2O/p-type GaAs(001)-(2x4)

Fermi Level

0.3-1.0Sample Bias (V)

dI/d

V/(

I/V

) (

a.u.

)dI

/dV

/(I/

V)

(a.

u.)

dI/d

V/(

I/V

) (

a.u.

)

Clean n-type GaAs(001)-(2x4)

0-1.4

dI/d

V/(

I/V

) (

a.u.

)

Main Chamber Equipped With:

LEEDAES

QMS STM

Filaments

Al2O3 Crucible

Ta Flag

Water Cooled Cu Collimator

Gate Valve

Experimental Setup

In2O3

In2OIn2O

In2O

In2O3(s)In2O(g)+O2(g)

Ga2O3(s)Ga2O(g)+O2(g)

GaAs(001)-(2x4)GaAs(001)-(2x4) Ga2O on GaAs(001)-(2x4) In2O on GaAs(001)-(2x4)

122 eV122 eV122 ev

Low Energy Electron Diffraction Images

Calculating Domain Sizes:

ex. Ga2O

‡ ‡

a

b

‡‡

b

a

Average Domain Size= (b/a)(4Å)b= distance between (1x1) spots

a=full width half maximum of the spot diameter

[110] 8.2 Å

19.2 Å[110]

Ave. Domain Sizes

Ga2O and In2O on GaAs(001)-(2x4) 410°C Dose/Monolayer Coverages

Ga2O/GaAs(001)-(2x4) In2O/GaAs(001)-(2x4)

16Å

0 300Å

300Å

0 300Å

300Å

8Å

ABSTRACT

 The surface structures formed upon deposition of Ga2O and In2O onto the technologically important As-

rich GaAs(001)-(2x4) surface have been studied using scanning tunneling microscopy (STM) and

spectroscopy (STS) and Low Energy Electron Diffraction (LEED), and the results are compared with

density functional theory (DFT) calculations. At sub-monolayer coverage, the initial bonding sites are

different for Ga2O and In2O adsorptions due to the ability of the incident species to surmount different

activation barriers for chemisorption. In2O first bonds in the trough between the arsenic dimer rows,

whereas Ga2O first inserts into the dimer rows. Although the initial bonding for both species is distinctly

different, at elevated surface temperatures, a (2x1) surface reconstruction is seen with LEED for both

Ga2O and In2O adsorptions. Although both oxides show (2x1) periodicity, Ga2O induces a larger step

density while In2O has much larger row spacing. Both oxides form crystalline charge balanced surface

reconstructions that are electronically unpinned: there are no states within the band gap. The surfaces are

unpinned because the oxides restore the Ga and As surface atoms to near bulk charge.

Michael HaleMichael Hale, Jonathan Sexton, Sang Yi, Darby Winn, and Andrew Kummel, Jonathan Sexton, Sang Yi, Darby Winn, and Andrew KummelUniversity of California, San DiegoUniversity of California, San Diego

9500 Gilman Dr. 9500 Gilman Dr. La Jolla, Ca. 92093-0358La Jolla, Ca. 92093-0358

Ga2O on GaAs(001)-(2x4) 410°C Dose/Low Coverage

As Ga O

8Å

[110]

[110]

Ga2O Inserts into Arsenic Dimer Pairs