Chalcogenide glasses structure

J.P. Kloock, L. Moreno, A. Bratov, S. Huachupoma, J. Xu, T. Wagner, T. Yoshinobu, Y. Ermolenko, Y.G. Vlasov and M.J. Schoning, PLD-pre-pared cadmium sensors based on chalcogenide glasses—ISFET, LAPS and pISE semiconductor structures, Sens. Actuators B Chem., 118 (2006) 149-155. 

The objective of this protocol is the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta205 as a sensor membrane, and for the cadmium-selective LAPS, use a Cd2+-selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterisation of the LAPS structure perform current vs. voltage (I/V) and constant current (CC) measurements. 

For the determination of the cadmium-ion concentration in aqueous solutions, prepare chalcogenide glass thin-film materials onto the half of the pH-sensitive LAPS structure (see Section 6.3.1). 

With the help of this plasma phase, which includes the stoichiometric proportion of the complex chalcogenide glass material, thin films of chalcogenide glass material can be deposited onto the LAPS structure [6,7]. 

Determine the thickness of the Cd2+-selective chalcogenide glass thin films to be about 950 nm (e.g., profilometric measurements by means of Sloan Dektak II). The pH- and cadmium-sensitive LAPS structure and the schematic measurement set-up are shown in Fig. 6.1. 

Chalcogenide glasses consist of long Se (or Te) chains bonded with Ge or As. In these the basic structural units are chains that are cross-linked by As or Ge. The structure of molten pure selenium and pure tellurium consists of... 

V. A. Funtikov, Eutectoidal Concept of Glass Structure and Its Application in Chalcogenide Semiconductor Glasses... 

V. S. Minaev, Concept of Polymeric Polymorphous-Crystalloid Structure of Glass and Chalcogenide Systems Structure and Relaxation of Liquid and Glass... 

The second term on the right hand side raises the interesting possibility of a defect that has a negative total correlation energy. This concept was introduced by Anderson (1975) and was first observed in the defect structure of chalcogenide glasses (Street and Mott 1975). 

Table 6.1. Comparison of the equilibrium effects in a-Si. H and chalcogenide glasses, in terms of the length scales of the structural units involved...

As shown by Tanaka,chalcogenide glasses are prone to photoinduced phenomena such as photorefractivity, photoexpansion, photofluidity, and so on which indicate that the local structure can be easily modified under suitable light irradiation. 

The last three chapters summarize unique structural and chemical features of a variety of glasses. They also provide an overview of the important aspects of the glass systems. Chapters 12 and 13 discuss respectively oxide and chalcogenide glasses particularly in view of their chemistry, structure and a number of special phenomena associated with them. In chapter 14, synthesis, structure and properties of halide, oxyhalide, oxynitride and metallic glasses are discussed. Some aspects of glass-like carbon have also been presented. 

The constraints model sketched above has a natural extension to it. In network forming multi-component glasses such as 432 (Ge-As-Se) chalcogenide glasses, locally there will be the regions of the structure where the average coordination, (mi) is lower than mo. Such regions are easily defonnable and are described as floppy, under constrained or... 

---