Growth and Raman spectroscopic characterization of As4S4 (II) single crystals
Introduction
Investigations of photochemical sensitivity in arsenic chalcogenides are important for fundamental sciences and for their practical applications in optical memories, optical switches, and fiber lasers. Tetra-arsenic tetrasulfide, As4S4, exists in four crystalline modifications. Many studies have been conducted on their crystal structures, spectroscopic properties, phase transitions, and stability fields of the As4S4 polymorphs: realgar (α-As4S4) [1], [2], [3], [4], [5], [6]; the high-temperature phase (β-As4S4) based on the same realgar-type molecule with different molecular packing [7], [8], [9], [10], [11], [12], [13]; pararealgar obtained by photo-induced phase transformation of both the realgar and the high-temperature phases [14], [15]; and As4S4 (II) phase, composed of the pararealgar-type molecule with different molecular arrangements [16]. The summary of crystal structural information is shown in Table 1. Because of the unique effect induced by photoexcitation, which is analogous to a domino effect [17], numerous studies have been made to date on the photo-induced phase transition from realgar-type molecule to pararealgar molecule [18], [19], [20], [21], [22], [23], [24], [25], [26], [27].
Although many studies have examined α-As4S4, β-As4S4, and pararealgar, very little information about the As4S4 (II) phase is available. Single crystals of the As4S4 (II) phase are synthesized by recrystallizing a quenched AsS melt from 500 to 600 °C [16]. To date, this is the only report describing the crystallization and structural characterization by X-ray diffraction analysis of this phase. Although Kutoglu [16] documented conditions under which As4S4 (II) phase single crystals have been grown, we have never obtained the crystals using this method. In the past thirty years, no reported study has examined the structure and optical properties of the As4S4 (II) phase.
This study is intended to reveal an appropriate crystal growth method of the As4S4 (II) phase. This paper reports the growth of As4S4 (II) single crystals by recrystallization of the pararealgar from CS2 solution. The crystals were subsequently characterized using powder and single crystal X-ray diffraction analyses. For this study, the Raman spectra of the As4S4 (II) phase were first measured on the flat surface of the single crystal under ambient conditions.
Section snippets
Experimental and results
According to Kutoglu [16], single crystals of As4S4 (II) phase were obtained from a quenched AsS melt as a starting substance. The method documented in the previous study [16] was attempted to synthesize As4S4 (II) single crystals, but the crystals were never obtained. The structure of As4S4 (II) phase comprises pararealgar-type molecules held together by van der Waals forces, which suggests that the pararealgar possessing the same molecular configuration is more effective as a precursor than
Summary
Single crystals of As4S4 (II) phase were grown using the dissolution–recrystallization method. No impurity phase was formed using this crystal growth method. Crystals obtained using this method exhibit a platelet-like form with well-developed faces (0 1 0) and (0 1¯ 0) with a size of several hundred micrometers square. The largest crystals were approximately 1 mm×1 mm×0.02 mm. As determined from X-ray diffraction analyses, the single crystals prepared in this study are highly homogeneous. This simple
Acknowledgments
This work was supported by a Grant-in-Aid for Young Scientists (B) (No. 19740325) from the Japan Society for the Promotion of Science. An anonymous reviewer is kindly acknowledged for improving the quality of the manuscript.
References (28)
- et al.
J. Chem. Thermodyn.
(1988) - et al.
Spectrochim. Acta
(1996) - et al.
Surf. Sci.
(2003) - et al.
Acta Crystallogr.
(1952) - et al.
Dokl. Akad. Nauk SSSR
(1963) Am. Mineral.
(1969)- et al.
Z. Kristallogr.
(1972) - et al.
Z. Anorg. Allg. Chem.
(1983) Am. Mineral.
(1970)- et al.
J. Inorg. Nucl. Chem.
(1970)