The sensitivity and peak areas of the characteristic elements in the full scan spectrum and that obtained by the argon ion sputtering method were compared. Four samples were submitted to this study, including AlP technical powder (85%), AlP tablets (55%), aluminum powder (95%) and red phosphorus (96%).
XPS for Aluminum Phosphide tablets
A 55% AlP tablet was used in duplicate for the full scan analysis of XPS. P (2p) has a binding energy of 133.7eV. Al (2p) has a binding energy of 74.4 eV (single peak) Minor impurities including sodium, calcium, magnesium, nitrogen and oxygen, etc. were found in this 55% tablet formulation. Aluminum (2p) has a binding energy of 74.5, while P (2p) (133.7eV) has a weak signal on the spectrum due to contamination(s) of the sphere.
The qualitative and quantitative composition of technical aluminum phosphide was studied employing X-ray photo-electron spectroscopy as well as gravimetric and gas volumetric methods in this research. AlN, Al, Al(OH)3, Mg2+ and As (below 0.04%) were found to be present, in addition to AlP, in the technical and formulated AlP products. Al(OH)3 is produced by the reaction of AlP with H2O. Some impurities are from the the raw materials. This conclusion was supported by analysis of the aluminum and red phosphorous. Additionally, Na (1s in XPS) and Ca (2p in XPS) etc were found in some amount in the raw materials.
The reaction of aluminum phosphide with water produces a white power and gaseous PH3. No reaction was observed between AlP and dry air. The solid reaction product could therefore be Al2O3, AlO(OH), and Al(OH)3. It is assumed that reaction with water vapor causes the growth of concentric layers of Al(OH)3. The mass of Al(OH)3 was determined by the thickness of these layers in XPS spectroscopy. The values of the concentration of Al(OH)3, and other impurities of the analyzed specimens in AlP technical were: Al(OH)3: 12%, Al: 1.1% and AlN: 3.5%, respectively.
X-ray photoelectron analysis showed a small signal for phosphorus in fresh specimens. This indicated that the presence of absorbing coatings that were thicker enough than 50 Angstroms. To determine precisely the phosphorus concentrations, the grains of the specimens were stripped of surface contaminations by argon ion sputtering. These results were consistent with the reporting of Mantler [
1], Moffitt [
4] and Chuan [
5] for similar researches for multi-layer films. It’s observed that signal intensities from oxygen and aluminum increased at first accompanying with the removal of the layer by about 0.5 – 1.0 μm. Oxygen signal decrease as a function of sputtering time, synchronously with the increase of the phosphorous signal from the AlP nucleus, while the aluminum signal which was considered to mainly due to AlP and Al(OH)
3, remains constant. Thus, by the argon ion sputtering technique, the main differences between the technical AlP and AlP products were identified semi-quantitatively as described.