Electronic structure of semiconductor oxides:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">InPO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, In(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">PO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">P</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">SiO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">AlPO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>, and Al(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">PO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> (1990)

The electronic structure of InP oxides, AlP oxides, and ${\mathrm{SiO}}_{2}$ is investigated both experimentally and theoretically. X-ray-photoemission valence-band spectra are compared with tight-binding calculations in order to analyze the different contributions to each spectrum. Oxygen-oxygen interactions must be included to explain the experimental features. A systematic analysis of the ${\mathrm{SiO}}_{2}$-${\mathrm{AlPO}}_{4}$-${\mathrm{InPO}}_{4}$ and ${\mathrm{InPO}}_{4}$-In(${\mathrm{PO}}_{3}$${)}_{3}$-${\mathrm{P}}_{2}$${\mathrm{O}}_{5}$ family evolution is made. The nature of the atomic states participating in the valence-band spectra is identified. The role of In and Al atoms in the valence band is analyzed, and we conclude that their influence is not negligible in the cases of ${\mathrm{InPO}}_{4}$ and ${\mathrm{AlPO}}_{4}$. We can distinguish two types of oxygen atoms in some oxides: ${\mathrm{O}}_{\mathrm{b}}$ bridging different ${\mathrm{PO}}_{4}$ tetrahedra, and ${\mathrm{O}}_{\mathrm{nb}}$ only linked to one P atom. We conclude that the presence or absence of ${\mathrm{O}}_{\mathrm{b}}$ has observable consequences in the XPS valence-band spectra.