Syntheses of Metal Chalcogenides Using Organometallic Methods
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SYNTHESES OF METAL CHALCOGENIDES USING ORGANOMETALLIC METHODS MICHAEL L. STEIGERWALD AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey, 07974
ABSTRACT The precursor method is being used increasingly in the preparation of solid state inorganic materials. Use of this general method allows the isolation of otherwise inaccessible phases and the preparation of known phases under much milder conditions. One approach which holds promise is the use of organometallic precursors for the preparation of both thin films and bulk samples of inorganic materials. In this paper I describe our syntheses of several metal chalcogenides from organometallic reagents.
INTRODUCTION The synthesis of inorganic solid state compounds is most typically achieved by combination of the proper stoichiometries of the elements as solids [1]. To insure complete interdiffusion of the solid reagents these reactions are usually conducted at high temperature. This can be a severe limitation. Lower processing temperatures allow the preparation of metastable phases and give wider latitude in the fabrication of complicated physical structures (heterostructures, quantum wells, etc.) which are unstable at higher temperatures. In part to avoid such harsh reaction conditions there has been increasing interest in the use of precursor methods [2]. The general technique here is not to combine the elements, but rather to combine molecular precursors to the elements such that when the precursors are heated or otherwise chemically treated the ancillary components are removed as the solid state compound is formed. Since the elements are intimately mixed in the "molecular' stage of the process the problem of the interdiffusion of the elements is removed and the low temperature synthesis is facilitated. Organometallic molecular compounds have features which make them attractive as precursors to solid state compounds. The most important of these is that they are the elements masked in molecular form, which can be dispersed molecularly in a variety of innocent solvents. This obviates elemental interdiffusion since suitable precursors for each element can be dispersed in the same solvent. When the solvent is subsequently removed the different precursors are left mixed on the molecular level. A second advantage is that there exists an extensive list of ligand systems in organometallic chemistry. The creative use of these ligand systems will allow molecular control over processing. As an example, with the proper choice of ligands precursor compounds can be made volatile. This is crucial for the application of organometallic methods to the preparation of thin films by vapor phase epitaxy. In this manuscript I will describe some of our recent work on the preparation and use of organometallic precursors in the synthesis of solid state compounds.
Mat. Res. Soc. Symp. Proc. Vol. 131. c1989 Materials Research Society
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I1-VI COMPOUNDS A serious impediment to the growth of thin-films of HgTe and CdTe by organometallic vapor phase epitaxy (OMVPE) has been t
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