Simulations of silver-doped germanium-selenide glasses and their response to radiation
- PDF / 2,754,744 Bytes
- 9 Pages / 595 x 794 pts Page_size
- 3 Downloads / 131 Views
NA NO EXPR ESS
Open Access
Simulations of silver-doped germanium-selenide glasses and their response to radiation Kiran Prasai and David A Drabold* Abstract Chalcogenide glasses doped with silver have many applications including their use as a novel radiation sensor. In this paper, we undertake the first atomistic simulation of radiation damage and healing in silver-doped Germanium-selenide glass. We jointly employ empirical potentials and ab initio methods to create and characterize new structural models and to show that they are in accord with many experimental observations. Next, we simulate a thermal spike and track the evolution of the radiation damage and its eventual healing by application of a simulated annealing process. The silver network is strongly affected by the rearrangements, and its connectivity (and thus contribution to the electrical conductivity) change rapidly in time. The electronic structure of the material after annealing is essentially identical to that of the initial structure. Keywords: Radiation damage; Chalcogenide glass; Dosimeter
Background Chalcogenide materials are among the most flexible and useful in current technology. Certain GeSbTe alloys are the basis of phase change memory technology [1] (now a credible alternative to conventional FLASH memory) and DVDs [2]. Amorphous Se is the active element for digital x-ray radiography [3], and metal-doped chalcogenide glasses are among the best known solid electrolytes or ‘fast ion conductors’ [4] and form the basis for another quite promising class of FLASH memory devices, ‘conducting bridge’ memory. The basic science of the material is just as interesting as the other phenomena such as the optomechanical effect [5] and photomelting [6]. Recently, a new application has emerged: the use of chalcogenide glasses for the detection or sensing of radiation (a dosimeter) [7,8]. The electrical conductivity is found to be well-correlated to radiation dose [9]. With annealing, the damage is readily reversed so that the device may be reused. This important discovery is presently empirically understood, suggesting the need for theoretical research both to understand the basic process and to aid in optimizing the materials for future device application.
In this paper, we undertake the first simulation to understand the atomistics of the response of chalcogenide glasses to highly energetic events. Like many other challenging material problems, we find it helpful to use multiple methods, in this case both empirical potentials, and ab initio techniques. We also have taken advantage of the contributions of others, such as the use of an appropriate ‘heat bath’ to handle the excess thermal energy after the thermal spike [10]. We detail the disordering process from a knock-on event to the subsequent recovery process. We show that the spike is indeed reversible upon annealing and discuss the electron states near the Fermi level - those responsible for the changes in (electronic) conduction after radiation exposure. The picture that emerges is that the el
Data Loading...
