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Approximation of the Density of States for Both Clean and O Adsorbed GaAs(001)-(2x4). Approximation of the Density of States for Ga 2 O on Both n - and p -type GaAs(001)-(2x4). Auger Electron Spectroscopy of In 2 O on GaAs(001)-(2x4). In 2 O on GaAs(001)-(2x4) 410 °C Dose/Low Coverage. - PowerPoint PPT Presentation
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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