To establish the validity of various proposed structural models, we have investigated the structure of the binary ${\mathrm{As}}_x{\mathrm{Se}}_{100-x}$ chalcogenide glass family $(x⩽40)$ by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the $4p$ lone pair electrons of Se and the $4p$ bonding states and $4s$ electrons of Se and As are identified in the top part of the band. The analysis of Se $3d$ and As $3d$ core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich ${\mathrm{As}}_x{\mathrm{Se}}_{100-x}$ bulk glasses. The results also indicate small deviations $(\sim 3–8\%)$ from this model, especially for glass compositions with short Se chains $(25<x⩽40)$. For example, the presence of As-As homopolar defect bonds in the stoichiometric ${\mathrm{As}}_{40}{\mathrm{Se}}_{60}$ and of Se-Se-Se fragments in a glass with composition $x=30$ is established.

The structure of homogeneous bulk As _x S_{100− x} (25 ≤ x ≤ 42) glasses, prepared by the conventional rocking–melting–quenching method, was investigated using high-resolution X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. It is shown that the main building blocks of their glass networks are regular AsS_3/2 pyramids and sulfur chains. In the S-rich domain, the existence of quasi-tetrahedral (QT) S = As(S_1/2)₃ units is deduced from XPS data, but with a concentration not exceeding ∼3–5% of total atomic sites. Therefore, QT units do not appear as primary building blocks of the glass backbone in these materials, and an optimally-constrained network may not be an appropriate description for glasses when x < 40. It is shown that, in contrast to Se-based glasses, the ‘chain-crossing’ model is only partially applicable to sulfide glasses.

The advantages and applications of chalcogenide glass (ChG) thin film photoresists for grayscale lithography are demonstrated. It is shown that the ChG films can be used to make ultrathin $(∼600nm)$, high-resolution grayscale patterns, which can find their application, for example, in IR optics. Unlike polymer photoresists, the IR transparent ChG patterns can be useful as such on the surface or can be used to transfer the etched pattern into silicon or other substrates. Even if the ChG is used as an etch mask for the silicon substrate, its greater hardness can achieve a greater etch selectivity than that obtained with organic photoresists. The suitability of ChG photoresists is demonstrated with inexpensive and reliable fabrication of ultrathin Fresnel lenses that are transparent in the visible as well as in the IR region. The optical functionality of the Fresnel lenses is confirmed. Application of silver photodissolution in grayscale lithography for microelectromechanical systems (MEMS) applications is also shown. A substrate to ChG/silver thickness etching ratio of $∼10$ is obtained for the transfer of patterns into silicon using reactive ion etching (RIE), more than a fivefold increase compared to traditional polymer photoresist.

The structure of binary ${\text{Ge}}_x{\text{Se}}_{100-x}$ chalcogenide glass family $\left(0\le x\le 30\right)$ is determined by high-resolution x-ray photoelectron spectroscopy (XPS). On the basis of compositional dependences of fitting parameters for Ge and Se core level XPS spectra, the ratio between edge- and corner-shared tetrahedra is determined. We find that this ratio for glasses with $20\le x\le 30$ is almost constant with a value same as for the high-temperature crystalline form of ${\text{GeSe}}_2$ .