Inorg. Chem. 2000, 39, 2061-2064
2061
Solvothermal Route to Tin Monoselenide Bulk Single Crystal with Different Morphologies Bin Li,† Yi Xie,*,† Jiaxing Huang,‡ and Yitai Qian† Structure Research Laboratory and Department of Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China ReceiVed August 11, 1999
Orthorhombic SnSe bulk single crystals with different morphologies were conveniently grown through solvothermal process at low temperature (180 °C). X-ray diffraction (XRD) patterns, scanning electronic microscope (SEM) images, electronic diffraction (ED), and X-ray photoelectron spectra (XPS) were used to characterize the products. In the solvothermal process, the solvent plays an important role in the growth of the single crystal. The morphology of the crystal is influenced not only by the kind of solvent but also by the concentration of the reactants in solvent. Single crystals with rodlike or platelike morphology can be conveniently obtained under controlled concentration of reactants in solvent.
Introduction The IV-VI intermetallic compounds SnSe and SnSe2 possess interesting semiconducting properties. SnSe belongs to the interesting class of isomorphic materials that are in many ways between two-dimensional (layer type) systems and threedimensional crystals, and it exhibits a strong anisotropy of optical properties.1 SnSe is a semiconductor with a band gap of about 1 eV and therefore should possess the potential to work as an efficient solar cell material.2 It is also of interest to holographic recording systems3 and electrical switching.4 The SnSe bulk single crystals have mainly been grown by the Bridgman method5,6 and vapor phase methods (such as the chemical vapor transport technique using ammonium chloride as a transporting agent,7 the close-tube-vapor-transport technique,8,9 and the direct vapor transport technique without transporting agent1). In those methods special and complicated devices are generally required and the crystal growth usually needs two steps: the formation of SnSe powders and the later crystal growth. Moreover, the growth temperature is high (>600 °C) and the temperature gradient has to be carefully controlled. Microcrystalline selenides can be prepared by the hydrothermal process at 260-312 °C and 100 atm.10 The high pressure * To whom correspondence should be addressed. Address: Department of Chemistry, University of Science & Technology of China, Hefei, Anhui 230026, P. R. China. Phone: 86-551-3603987. Fax: 86-551-3631760. E-mail:
[email protected]. † Structure Research Laboratory and Department of Chemistry. ‡ Department of Chemical Physics. (1) Agarwal, A.; Patel, P. D.; Lakshminarayana, D. J. Cryst. Growth 1994, 142, 344. (2) Loferski, J. J. J. Appl. Phys. 1956, 27, 777. (3) Valiukonis, G.; Guseinova, D. A.; Krivaite, G.; Sileika, A. Phys. Status Solidi B 1986, 135, 299. (4) Chu, D.; Walser, R. M.; Bene, R. W.; Courtney, T. H. Appl. Phys. Lett. 1974, 24, 479. (5) Agnihotri, O. P.; Jain, A. K.; Gupta, B. K. J. Cryst. Growth 1979, 46, 491. (6) Bhatt, V. P.; Gireesan, K.; Pandya, G. R. J. Cryst. Growth 1989, 96, 649. (7) Agarwal, A. J. Cryst. Growth 1998, 183, 347. (8) Maier, H.; Daniel, D. R. J. Elect. Mater. 1977, 6, 693. (9) Yu, J. G.; Yue, A. S.; Stafsudd, O. M. J. Cryst. Growth 1981, 54, 248. (10) Cambi, L.; Elli, M. Chim. Ind. 1968, 50, 94.
makes the thermal process less safe. Recently, the solvothermal technique, which is carried out at low temperature and does not require organometallic precursors, has been developed as a mild and effective route to synthesize novel materials.11 Such a process has allowed for the synthesis of several kinds of nanocrystalline selenides.12-14 However, no reports on the preparation of single crystalline selenides by this mild method were found. Here, we extend the solvothermal technique to prepare single crystalline SnSe. We successfully obtained two kinds of SnSe bulk single crystals with rodlike and platelike morphologies under mild conditions (180 °C and less than 30 atm11) and found that the morphologies are influenced not only by the solvent but also by the reactant concentration. Inorganic materials with different morphologies, which have the same chemical composition, may exhibit different physical properties.15 Therefore, the synthesis of these materials would be particularly interesting. Moreover, thin platelets (
