A method based on the Langmuir equation for the estimation of vapour pressure and enthalpy of sublimation of subliming compounds is described. The variable temperature thermogravimetric/differential thermogravimetric (TG/DTG) curve of benzoic acid is used to arrive at the instrument parameters. Employing these parameters, the vapour pressuretemperature curves are derived for salicylic acid and camphor from their TG/DTG curves. The values match well with vapour pressure data in the literature, obtained by effusion methods. By employing the Clausius-Clapeyron equation, the enthalpy of sublimation could be calculated. Extending the method further, two precursors for metal-organic chemical vapour deposition (MOCVD) of titanium oxide bis-isopropyl bis tert-butyl 2-oxobutanoato titanium, Ti(O i Pr) 2 (tbob) 2 , and bis-oxo-bis-tertbutyl 2-oxobutanoato titanium, [TiO(tbob) 2 ] 2 , have been evaluated. The complex Ti(O i Pr) 2 (tbob) 2 is found to be a more suitable precursor. This approach can be helpful in quickly screening for the suitability of a compound as a CVD precursor.

Articles you may be interested inCharacterizations of Ga-doped ZnO films on Si (111) prepared by atmospheric pressure metal-organic chemical vapor deposition Identification of important growth parameters for the development of high quality Al x > 0.5 Ga 1 − x N grown by metal organic chemical vapor deposition J. Vac. Sci. Technol. A 25, 441 (2007); 10.1116/1.2713409 Ductile relaxation in cracked metal-organic chemical-vapor-deposition-grown AlGaN films on GaN

Thin films of vanadium dioxide have been deposited on glass by low pressure metal-organic chemical vapour deposition using the b-diketonate complex, vanadyl acetylacetonate, as the precursor. It is found that nearly monophasic, monoclinic VO 2 (M) films are formed in the narrow temperature range 475-520 uC, films formed outside this range comprising significant proportions of other vanadium oxide phases beside VO 2 (M). The microstructure of these well-crystallized films varies significantly with temperature in this range. Films grown at 475 uC are dense and have a very strong (200) orientation. At 520 uC, films are somewhat porous, and display little preferred orientation. Film microstructure influences the semiconductor-metal transition noticeably. Films deposited at 475 uC have a large change in resistance at 66 uC, and display a small temperature hysteresis in the transition. The transition temperature in films grown at 520 uC is higher (72 uC), whereas the change in resistance is smaller and the hysteresis larger. An attempt has been made to understand the unusual microstructure of VO 2 films grown on glass substrates. The variation in the phase transition characteristics is interpreted in terms of the observed film microstructure. The thermal properties of the CVD precursor are also reported.

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We report a new method for quantitative estimation of graphene layer thicknesses using high contrast imaging of graphene films on insulating substrates with a scanning electron microscope. By detecting the attenuation of secondary electrons emitted from the substrate with an in-column low-energy electron detector, we have achieved very high thickness-dependent contrast that allows quantitative estimation of thickness up to several graphene layers. The nanometer scale spatial resolution of the electron micrographs also allows a simple structural characterization scheme for graphene, which has been applied to identify faults, wrinkles, voids, and patches of multilayer growth in large-area chemical vapor deposited graphene. We have discussed the factors, such as differential surface charging and electron beam induced current, that affect the contrast of graphene images in detail.

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