Structure and photoinduced structural changes in nonstoichiometric a -As sub x S sub 1 minus x : A study by x-ray-absorption fine structure
- Department of Physics, North Carolina State University, Raleigh, North Carolina 27695-8202 (United States)
X-ray-absorption fine-structure data show that chemical ordering plays an important role in nonstoichiometric amorphous ({ital a}-)As{sub {ital x}}S{sub 1{minus}{ital x}} films at 0.4{le}{ital x}{lt}=0.5. The mixture of different chemical bonding behaviors of As-S and As-As in an {ital a}-As{sub 2}S{sub 3} random covalent network and an {ital a}-As{sub 4}S{sub 4} disordered molecular solid lead the structure to a more disordered state for 0.4{lt}{ital x}{lt}0.5. In particular, the structure at a composition around {ital x}=0.43 in {ital a}-As{sub {ital x}}S{sub 1{minus}{ital x}} represents a maximum of flexibility. Photoillumination results in (1) a more disordered state as indicated by an increase in the static Debye-Waller factors (which are related to the creation of As-As homopolar bonds) and (2) modifications in the network structure, such as the increase of the As-As radial distances in the second shells. In nonstoichiometric material, the presence of As{sub 4}S{sub 4} molecules in the As{sub 2}S{sub 3} network tends to break up this network into small segments. This decoupling of pieces of the As{sub 2}S{sub 3} network (composed of S-bridged AsS{sub 3} pyramids and As-As wrong bonds) may lead to increased steric freedom that is related to a more disordered state that appears to be associated with photoinduced structural changes in amorphous arsenic sulfide.
- DOE Contract Number:
- FG05-89ER45384; AC02-76CH00016
- OSTI ID:
- 7018137
- Journal Information:
- Physical Review, B: Condensed Matter; (United States), Vol. 46:7; ISSN 0163-1829
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARSENIC SULFIDES
MICROSTRUCTURE
ABSORPTION SPECTRA
AMORPHOUS STATE
CHEMICAL BONDS
FILMS
LASER RADIATION
PHYSICAL RADIATION EFFECTS
STOICHIOMETRY
X RADIATION
ARSENIC COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
RADIATION EFFECTS
RADIATIONS
SPECTRA
SULFIDES
SULFUR COMPOUNDS
360602* - Other Materials- Structure & Phase Studies