Growth without Postannealing of Monoclinic VO2 Thin Film by Atomic Layer Deposition Using VCl4 as Precursor

Vanadium dioxide (VO2) is a multifunctional material with semiconductor-to-metal transition (SMT) property. Organic vanadium compounds are usually employed as ALD precursors to grow VO2 films. However, the as-deposited films are reported to have amorphous structure with no significant SMT property, therefore a postannealing process is necessary for converting the amorphous VO2 to crystalline VO2. In this study, an inorganic vanadium tetrachloride (VCl4) is used as an ALD precursor for the first time to grow VO2 films. The VO2 film is directly crystallized and grown on the substrate without any postannealing process. The VO2 film displays significant SMT behavior, which is verified by temperature-dependent Raman spectrometer and four-point-probing system. The results demonstrate that the VCl4 is suitably employed as a new ALD precursor to grow crystallized VO2 films. It can be reasonably imagined that the VCl4 can also be used to grow various directly crystallized vanadium oxides by controlling the ALD-process parameters.

Single-Source Precursors to Vanadium Nitride Thin Films

Vanadium nitride films reflect infrared radiation and are candidates for solar control coatings for glass. Herein we report our efforts to prepare new precursors to vanadium nitride coatings. Treatment of vanadium tetrachloride with primary alkylamines in dichloromethane affords vanadium chloride amides of the empirical formula [VCI2(NHR)2(NH2R)2]. The characterization and properties of these compounds is presented. The complexes [VC12(NHR)2(NH2R)2] can be sublimed at ca. 100°C (0.1 mmHg) and serve as single-source precursors to vanadium carbonitride films. Films have been deposited in the temperature range of 400-600°C on glass and silicon substrates. The film properties and characterization will be overviewed.