Group III Metal Sulfide Thin Films From Single-Source Precursors by Chemical Vapor Deposition (CVD) Techniques
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Single-source precursors have often been used for the deposition of group 13 chalcogenide thin films (i.e. both the metal and chalcogen atoms are contained within the precursor complex); a number of different chalcogen containing ligands have been employed for the preparation of such precursor complexes, including thiolates, [3,4], selenolates, [5], thiocarboxylates, [6], thiocarbonates, [7], dithiocarbamates, [8,9] and diselenocarbamates [10]. Recently, we have reported the deposition of indium sulfide (P3-In2S3) and gallium sulfide (GaS) thin films by LP-MOCVD and AACVD, grown from novel indium and gallium monothiocarbamato complexes, In(SOCNEt 2)3, [11], In(SOCN'Pr 2)3, [12] and Ga(SOCNEt 2 )3 [13]. Herein we report the deposition of gallium sulfide thin films (CC-Ga 2S3) deposited on GaAs(l 11) single crystal substrates using the metal dithiocarbamato complexes, Ga(S 2CNMeEt) 3, Ga(S 2CNMeBu) 3, Ga(S 2CNMeHex) 3 by LP-MOCVD and films of indium sulfide (P-In 2S3 ) deposited on glass using In(S 2CNMeHex) 3 by AACVD. We have also continued our investigations into monothiocarbamato systems and report the deposition of cubic-In2 S3 thin film from the di-iso-butylmonothiocarbamato complex, In(SOCN'Bu 2)3, on borosilicate glass substrates by LP-MOCVD.
127 Mat. Res. Soc. Symp. Proc. Vol. 606 © 2000 Materials Research Society
EXPERIMENTAL Chemicals Carbon disulfide, carbonyl sulfide, sodium hydroxide and secondary amines were purchased from Aldrich chemical Company Ltd and methanol and THF were from BDH. These were used with no further purification. Gallium (III) sulfide and indium (III) sulfide were gifts from Epichem Ltd. Instrumentation IH NMR spectroscopy was carried out on a Bruker AM270 Fourier-transform instrument. Elemental analysis was performed by the Imperial College Chemistry Departmental Service. All manipulations and reactions were carried out in an inert atmosphere using Schlenk techniques and a vacuum line. X-Ray diffraction (XRD) patterns were measured using a Siemens D500 series automated powder diffractometer using Cu-Kc- (radiation at 40 kV/40 mA) with a secondary graphite crystal monochromator. Samples were mounted on a glass slide (5 x 5cm) and scanned from 10 -60 o in steps of 0.040 with a count time of 2 s. Energy Dispersive X-ray microanalysis (EDAX) was performed on a LINK QX2000 energy dispersive X-ray microanalysis unit. For scanning electron microscopy (SEM) the samples were gold-coated using a Balzers SCD 030 sputter coating unit before study with a JEOL JEM-1200 EX-I1 microscope. Preparation of single-source precursors The single-source precursors, In(S 2CNMeHex) 3 , In(SOCN'Bu 2)3, Ga(S 2CNMeHex) 3, Ga(S 2CNMeBu) 3 and Ga(S 2CNMeEt) 3 have been prepared by the literature method [9,11] and were characterized by elemental analysis, IR and NMR. Preparation of thin films by AACVD Typically, In(S 2CNMeHex) 3 (0.3 g) was dissolved in THF (30 ml) at room temperature, and injected into the growth apparatus, with the substrate at various temperatures. The system was allowed to run for 1 hr., wi
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