Bismuth telluride (Bi2Te3) was analyzed using x-ray photoelectron spectroscopy. A freshly exfoliated, oxygen-free flake was analyzed. Spectral regions for O 1s, Te 3d, C 1s, Bi 4f, Bi 5d, and Te 4d were acquired. Bulk quantitative analyses by x-ray fluorescence, inductively coupled plasma-mass spectrometry, and x-ray diffraction indicated that the material was stoichiometric, contained low concentrations of impurities, and was phase pure, respectively.
Accession #: 01551
Technique: XPS
Host Material: Bi2Te3
Instrument: Physical Electronics VersaProbe II
Major Elements in Spectra: Bi, Te, C
Minor Elements in Spectra: None detected
Published Spectra: 8
Spectra in Electronic Record: 8
Spectral Category: Comparison
INTRODUCTION
Transition metal dichalcogenides are a potentially important class of materials owning to their unique physical, electronic, and optical properties. Bismuth telluride is a topological insulator exhibiting different surface and bulk conduction properties making them promising materials for future electronic devices (Refs. 1–4).
SPECIMEN DESCRIPTION (ACCESSION #01551)
Host Material: Bi2Te3 polycrystalline
CAS Registry #: 1304-82-1
Host Material Characteristics: Homogeneous; solid; polycrystalline; topological insulator; other
Chemical Name: Bismuth telluride
Source: Alfa Aesar
Host Composition: Bi2Te3
Form: Polycrystalline solid
Structure: Hexagonal
History and Significance: Fresh layers were mechanically exfoliated using 3M™ double-sided adhesive tape. The tape with Bi2Te3 flakes was then placed on Si (100) and immediately introduced to the vacuum system. A total of six flakes were analyzed. The one with the lowest O% and C% is presented here. Carbon was present at ∼14%; oxygen was not detected. The Te:Bi ratio and peak positions and shapes were consistent among the multiple measurements with the exception of minor evidence of oxidation on selected flake (data not included). A separate flake was chosen for the wide scan analyses (includes valence band). These experiments were repeated using a different XPS instrument (UTD) and both ex situ and in situ exfoliation. Peak positions and shapes were identical to these within <0.1 eV in all cases. In situ exfoliation resulted in lower levels of atmospheric contaminants (O and C).
As Received Condition: Flaky multilayered solid
Analyzed Region: Exfoliated flake of host
Ex Situ Preparation/Mounting: Double-sided adhesive tape pull
In Situ Preparation: See comment in History
Charge Control: Low energy electron flood and low energy Ar+ flood
Temp. During Analysis: 300 K
Pressure During Analysis: 1 × 10−6 Pa
Preanalysis Beam Exposure: 60 s
INSTRUMENT DESCRIPTION
Manufacturer and Model: Physical Electronics VersaProbe II
Analyzer Type: Spherical sector
Detector: Channeltron
Number of Detector Elements: 8
INSTRUMENT PARAMETERS COMMON TO ALL SPECTRA
Spectrometer
Analyzer Mode: Constant pass energy
Throughput (T = EN): N = 0
Excitation Source Window: None
Excitation Source: Al Kα monochromatic
Source Energy: 1486.6 eV
Source Strength: 51.5 W
Source Beam Size: 200 × 200 μm2
Signal Mode: Multichannel direct
Geometry
Incident Angle: 0°
Source-to-Analyzer Angle: 45°
Emission Angle: 45°
Specimen Azimuthal Angle: 0°
Acceptance Angle from Analyzer Axis: 0°
Analyzer Angular Acceptance Width: 20° × 20°
Ion Gun
Manufacturer and Model: Physical Electronics
Energy: 2000 eV
Current: 0.001 mA
Current Measurement Method: Faraday cup
Sputtering Species: Ar+
Spot Size (unrastered): 500 μm
Raster Size: 2000 × 2000 μm2
Incident Angle: 45°
Polar Angle: 45°
Azimuthal Angle: 45°
Comment: Monotonic argon sputtering was performed with a differentially pumped ion gun for the calibration spectra only.
DATA ANALYSIS METHOD
Energy Scale Correction: The binding energy scale was referenced to Te 3d5/2 = 572.0 eV (Ref. 1).
Recommended Energy Scale Shift: +2.125 eV
Peak Shape and Background Method: Iterated Shirley background subtraction used on Bi 4f and Te 4d for quantification.
Quantitation Method: Quantification was done using Scofield-inelastic mean free path corrected relative sensitivity factor from casaxps version 2.3.19rev1.0k.
ACKNOWLEDGMENT
This study is based upon research conducted at The Pennsylvania State University Two-Dimensional Crystal Consortium—Materials Innovation Platform (2DCC-MIP) which is supported by NSF cooperative agreement No. DMR-1539916.
