Arsenic

Arsenic • Metalloid

Primary XPS region: As3d
Overlapping regions: Ta5p_1/2
Binding energies of common chemical states:

Chemical state	Binding energy As3p_5/2
GaAs	40.8 eV
As₂O₃	44.1 eV
As³⁺ (GaAs native oxide)	44.8 eV
As⁵⁺ (GaAs native oxide)	45.6 eV

As₂O₃ charge referenced to C1s peak at 284.8eV. GaAs oxides charge referenced to GaAs at 40.8eV.

Experimental information

As₂O₃ sublimes in vacuum.
As⁵⁺ may degrade under X-rays, forming As³⁺ as a by-product.
- Minimize acquisition time where possible or collect data from several different locations on the sample (with very short acquisition times) and integrate the data.

Interpretation of XPS spectra

As3d peak has overlapping spin-orbit components (Δ=0.7eV, intensity ratio=0.7).
As LMM peaks (between 150eV-350eV) overlap with many XPS peaks from other elements.

Shallow As implants can be profiled with 200eV or 500eV Ar+.
- Typically, most of implant is within XPS sampling depth, but implant tail goes beyond XPS sampling depth.

‹Metalloid Elements

Table of Elements

About this element

Symbol: As
Date of discovery: ancient times
Name origin: Greek arsenikos; Latin arsenicum
Appearance: gray
Discoverer: unknown
Obtained from: mispickel

Melting point: 1090 K
Boiling point: 886 K
Density[kg/m³]: 5727
Molar volume: 12.95 × 10^-6 m³/mol
Protons/Electrons: 33
Neutrons: 42
Shell structure: 2,8,18,5
Electron configuration: [Ar]3d104s24p3
Oxidation state: ±3,5
Crystal structure: rhombohedral

Arsenic, a poisonous metalloid, is characteristically very similar to phosphorus, so much so that the element can be partially substituted for it in biochemical reactions. Arsenic and some of its compounds convert to a gaseous form and can rapidly oxidize to arsenic oxide, subliming directly upon heating. During the Bronze Age, arsenic was used as an impurity in the bronze to make the alloy harder. In Victorian times, women used arsenic as a complexion enhancer for their face. Fatalities occur when the toxic arsenic is handled improperly. Serious human and animal poisonings have occurred in recent years due to ingestion of arsenic – either directly or indirectly – from wood treated with copper arsenate. The most serious risk occurs when the treated wood is burned.

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