Structure and photoinduced structural changes in nonstoichiometric a -As sub x S sub 1 minus x : A study by x-ray-absorption fine structure

Journal Article · Sat Aug 15 04:00:00 EDT 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.46.3817· OSTI ID:7018137

Zhou, W; Paesler, M A; Sayers, D E ^[1]

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1. 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), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 46:7; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
ABSORPTION SPECTRA
AMORPHOUS STATE
ARSENIC COMPOUNDS
ARSENIC SULFIDES
CHALCOGENIDES
CHEMICAL BONDS
CRYSTAL STRUCTURE
ELECTROMAGNETIC RADIATION
FILMS
IONIZING RADIATIONS
LASER RADIATION
MICROSTRUCTURE
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
RADIATIONS
SPECTRA
STOICHIOMETRY
SULFIDES
SULFUR COMPOUNDS
X RADIATION