2D bismuth telluride analyzed by XPS

Shallenberger, Jeffrey R.; Smyth, Christopher M.; Addou, Rafik; Wallace, Robert M.

doi:10.1116/1.5120015

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 = E^N): N = 0

Excitation Source Window: None

Excitation Source: Al K_α 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 3d_5/2 = 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.

SPECTRAL FEATURES TABLE

Spectrum ID #	Element/Transition	Peak Energy (eV)	Peak Width FWHM (eV)	Peak Area (eV counts/s)	Sensitivity Factor	Concentration (at. %)	Peak Assignment
01551-02	Bi 5d_5/2	24.3	0.83	…	…	…	Bi₂Te₃
01551-02	Bi 5d_3/2	27.3	0.92	…	…	…	Bi₂Te₃
01551-02	Te 4d	39.4	0.79	31 592	1.482	51.6	Bi₂Te₃
01551-02	Te 4d_5/2	32.7	0.56	…	…	…	Bi₂Te₃
01551-02	Te 4d_3/2	34.8	0.56	…	…	…	Bi₂Te₃
01551-03	Bi 4f	157.2	0.89	140 028	9.842	34.4	Bi₂Te₃
01551-03	Bi 4f_7/2	157.2	0.89	…	…	…	Bi₂Te₃
01551-03	Bi 4f_5/2	162.6	0.94	…	…	…	Bi₂Te₃
01551-04	Te 3d_5/2	572.0	0.93	…	…	…	Bi₂Te₃
01551-04	Te 3d_3/2	582.4	0.91	…	…	…	Bi₂Te₃
01551-05	C 1s	284.4	1.15	1 818	0.344	13.9	Contaminant
01551-06	C, Bi, Te	…	…	…	…	…	Bi₂Te₃
01551-07	Valence	…	…	…	…	…	Bi₂Te₃

Spectrum ID #	Element/Transition	Peak Energy (eV)	Peak Width FWHM (eV)	Peak Area (eV counts/s)	Sensitivity Factor	Concentration (at. %)	Peak Assignment
01551-02	Bi 5d_5/2	24.3	0.83	…	…	…	Bi₂Te₃
01551-02	Bi 5d_3/2	27.3	0.92	…	…	…	Bi₂Te₃
01551-02	Te 4d	39.4	0.79	31 592	1.482	51.6	Bi₂Te₃
01551-02	Te 4d_5/2	32.7	0.56	…	…	…	Bi₂Te₃
01551-02	Te 4d_3/2	34.8	0.56	…	…	…	Bi₂Te₃
01551-03	Bi 4f	157.2	0.89	140 028	9.842	34.4	Bi₂Te₃
01551-03	Bi 4f_7/2	157.2	0.89	…	…	…	Bi₂Te₃
01551-03	Bi 4f_5/2	162.6	0.94	…	…	…	Bi₂Te₃
01551-04	Te 3d_5/2	572.0	0.93	…	…	…	Bi₂Te₃
01551-04	Te 3d_3/2	582.4	0.91	…	…	…	Bi₂Te₃
01551-05	C 1s	284.4	1.15	1 818	0.344	13.9	Contaminant
01551-06	C, Bi, Te	…	…	…	…	…	Bi₂Te₃
01551-07	Valence	…	…	…	…	…	Bi₂Te₃

ANALYZER CALIBRATION TABLE

Spectrum ID #	Element/Transition	Peak Energy (eV)	Peak Width FWHM (eV)	Peak Area (eV counts/s)	Sensitivity Factor	Concentration (at. %)	Peak Assignment
…	Au 4f	83.9	0.75	89 124	…	…	Au°
…	Ag 3d	368.1	0.65	96 772	…	…	Ag°
…	Cu 2p_3/2	932.6	0.91	67 784	…	…	Cu°

Spectrum ID #	Element/Transition	Peak Energy (eV)	Peak Width FWHM (eV)	Peak Area (eV counts/s)	Sensitivity Factor	Concentration (at. %)	Peak Assignment
…	Au 4f	83.9	0.75	89 124	…	…	Au°
…	Ag 3d	368.1	0.65	96 772	…	…	Ag°
…	Cu 2p_3/2	932.6	0.91	67 784	…	…	Cu°

GUIDE TO FIGURES

Spectrum (Accession) #	Spectral Region	Voltage Shift^a	Multiplier	Baseline	Comment #^b
01551-01	Survey	…	…	…	1
01551-02	Bi 5d–Te 4d	−2.125	…	…	1
01551-03	Bi 4f	−2.125	…	…	1
01551-04	Te 3d	−2.125	…	…	1
01551-05	C 1s	−2.125	…	…	1
01551-06	Wide	−2.125	…	…	1
01551-07	Valence	−2.125	…	…	1

Spectrum (Accession) #	Spectral Region	Voltage Shift^a	Multiplier	Baseline	Comment #^b
01551-01	Survey	…	…	…	1
01551-02	Bi 5d–Te 4d	−2.125	…	…	1
01551-03	Bi 4f	−2.125	…	…	1
01551-04	Te 3d	−2.125	…	…	1
01551-05	C 1s	−2.125	…	…	1
01551-06	Wide	−2.125	…	…	1
01551-07	Valence	−2.125	…	…	1

^a

Voltage shift of the archived (as-measured) spectrum relative to the printed figure. The figure reflects the recommended energy scale correction due to a calibration correction, sample charging, flood gun, or other phenomenon.

^b

1: Bi₂Te₃ exfoliated flake.

. Accession #01551-01Host Material:Bi2Te3Technique:XPSSpectral Region:SurveyInstrument:Physical Electronics VersaProbe IIExcitation Source:Al Kα monochromaticSource Energy:1486.6 eVSource Strength:51 WSource Size:0.2× 0.2 mm2Analyzer Type:Spherical sector analyzerIncident Angle:0°Emission Angle:45°Analyzer Pass Energy:187.85 eVAnalyzer Resolution:2.35 eVTotal Signal Accumulation Time:325 sTotal Elapsed Time:325 sNumber of Scans:2Effective Detector Width:24.0 eV

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Accession #	01551-01
Host Material:	Bi₂Te₃
Technique:	XPS
Spectral Region:	Survey
Instrument:	Physical Electronics VersaProbe II
Excitation Source:	Al K_α monochromatic
Source Energy:	1486.6 eV
Source Strength:	51 W
Source Size:	0.2× 0.2 mm²
Analyzer Type:	Spherical sector analyzer
Incident Angle:	0°
Emission Angle:	45°
Analyzer Pass Energy:	187.85 eV
Analyzer Resolution:	2.35 eV
Total Signal Accumulation Time:	325 s
Total Elapsed Time:	325 s
Number of Scans:	2
Effective Detector Width:	24.0 eV

Accession #	01551-01
Host Material:	Bi₂Te₃
Technique:	XPS
Spectral Region:	Survey
Instrument:	Physical Electronics VersaProbe II
Excitation Source:	Al K_α monochromatic
Source Energy:	1486.6 eV
Source Strength:	51 W
Source Size:	0.2× 0.2 mm²
Analyzer Type:	Spherical sector analyzer
Incident Angle:	0°
Emission Angle:	45°
Analyzer Pass Energy:	187.85 eV
Analyzer Resolution:	2.35 eV
Total Signal Accumulation Time:	325 s
Total Elapsed Time:	325 s
Number of Scans:	2
Effective Detector Width:	24.0 eV

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Accession #	01551-01
Host Material:	Bi₂Te₃
Technique:	XPS
Spectral Region:	Survey
Instrument:	Physical Electronics VersaProbe II
Excitation Source:	Al K_α monochromatic
Source Energy:	1486.6 eV
Source Strength:	51 W
Source Size:	0.2× 0.2 mm²
Analyzer Type:	Spherical sector analyzer
Incident Angle:	0°
Emission Angle:	45°
Analyzer Pass Energy:	187.85 eV
Analyzer Resolution:	2.35 eV
Total Signal Accumulation Time:	325 s
Total Elapsed Time:	325 s
Number of Scans:	2
Effective Detector Width:	24.0 eV

Accession #	01551-01
Host Material:	Bi₂Te₃
Technique:	XPS
Spectral Region:	Survey
Instrument:	Physical Electronics VersaProbe II
Excitation Source:	Al K_α monochromatic
Source Energy:	1486.6 eV
Source Strength:	51 W
Source Size:	0.2× 0.2 mm²
Analyzer Type:	Spherical sector analyzer
Incident Angle:	0°
Emission Angle:	45°
Analyzer Pass Energy:	187.85 eV
Analyzer Resolution:	2.35 eV
Total Signal Accumulation Time:	325 s
Total Elapsed Time:	325 s
Number of Scans:	2
Effective Detector Width:	24.0 eV

. . Accession #: 01551-02. Host Material: Bi2Te3. Technique: XPS. Spectral Region: Bi 5d, Te 4d. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 51 W. Source Size: 0.2 × 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 327 s. Total Elapsed Time: 1373 s. Number of Scans: 6. Effective Detector Width: 3.7 eV

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Accession #: 01551-02
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: Bi 5d, Te 4d

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 51 W
Source Size: 0.2 × 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 327 s
Total Elapsed Time: 1373 s
Number of Scans: 6
Effective Detector Width: 3.7 eV

. . Accession #: 01551-03. Host Material: Bi2Te3. Technique: XPS. Spectral Region: Bi 4f. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 51 W. Source Size: 0.2 × 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 193 s. Total Elapsed Time: 1373 s. Number of Scans: 6. Effective Detector Width: 3.7 eV

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Accession #: 01551-03
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: Bi 4f

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 51 W
Source Size: 0.2 × 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 193 s
Total Elapsed Time: 1373 s
Number of Scans: 6
Effective Detector Width: 3.7 eV

. . Accession #: 01551-04. Host Material: Bi2Te3. Technique: XPS. Spectral Region: Te 3d. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 50 W. Source Size: 0.2 × 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 7560 s. Total Elapsed Time: 1373 s. Number of Scans: 6. Effective Detector Width: 3.7 eV

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Accession #: 01551-04
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: Te 3d

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 50 W
Source Size: 0.2 × 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 7560 s
Total Elapsed Time: 1373 s
Number of Scans: 6
Effective Detector Width: 3.7 eV

. . Accession #: 01551-05. Host Material: Bi2Te3. Technique: XPS. Spectral Region: C 1s. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 51 W. Source Size: 0.2 × 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 1373 s. Total Elapsed Time: 9900 s. Number of Scans: 8. Effective Detector Width: 3.75 eV

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Accession #: 01551-05
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: C 1s

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 51 W
Source Size: 0.2 × 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 1373 s
Total Elapsed Time: 9900 s
Number of Scans: 8
Effective Detector Width: 3.75 eV

. . Accession #: 01551-06. Host Material: Bi2Te3. Technique: XPS. Spectral Region: C1s, Bi 4f, Bi 5d, Te 4d and valence. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 51 W. Source Size: 0.2 × 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 6600 s. Total Elapsed Time: 9817 s. Number of Scans: 6. Effective Detector Width: 3.7 eV

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Accession #: 01551-06
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: C1s, Bi 4f, Bi 5d, Te 4d and valence

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 51 W
Source Size: 0.2 × 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 6600 s
Total Elapsed Time: 9817 s
Number of Scans: 6
Effective Detector Width: 3.7 eV

. . Accession #: 01551-07. Host Material: Bi2Te3. Technique: XPS. Spectral Region: Valence band. Instrument: Physical Electronics VersaProbe II. Excitation Source: Al Kα monochromatic. Source Energy: 1486.6 eV. Source Strength: 50 W. Source Size: 0.2× 0.2 mm2. Analyzer Type: Spherical sector. Incident Angle: 0°. Emission Angle: 45°. Analyzer Pass Energy: 29.35 eV. Analyzer Resolution: 0.75 eV. Total Signal Accumulation Time: 1140 s. Total Elapsed Time: 9817 s. Number of Scans: 6. Effective Detector Width: 3.7 eV

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Accession #: 01551-07
Host Material: Bi₂Te₃
Technique: XPS
Spectral Region: Valence band

Instrument: Physical Electronics VersaProbe II
Excitation Source: Al K_α monochromatic
Source Energy: 1486.6 eV
Source Strength: 50 W
Source Size: 0.2× 0.2 mm²
Analyzer Type: Spherical sector
Incident Angle: 0°
Emission Angle: 45°
Analyzer Pass Energy: 29.35 eV
Analyzer Resolution: 0.75 eV
Total Signal Accumulation Time: 1140 s
Total Elapsed Time: 9817 s
Number of Scans: 6
Effective Detector Width: 3.7 eV

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.

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Author(s)

2D bismuth telluride analyzed by XPS

INTRODUCTION

SPECIMEN DESCRIPTION (ACCESSION #01551)

INSTRUMENT DESCRIPTION