David J. Houlton

Growth of ZnO by MOCVD using alkylzinc alkoxides as single-source precursors

Thin films of ZnO have been grown by low-pressure MOCVD using methylzinc isopropoxide, MeZn(OPri), and methylzinc tert-butoxide, MeZn(OBut), in the absence of an added oxygen source. The films were grown on to glass substrates in the temperature range 250–400 °C with growth rates of between 0.2 and 4.4 µm h–1.

The Gas‐Sensing Properties of Tin Oxide Thin Films Deposited by Metallorganic Chemical Vapor Deposition

A series of undoped SnO 2 films was grown by metallorganic chemical vapor deposition (MOCVD) from an Sn(O t Bu) 4 precursor. The characterization of their CO- and H 2 O-gas sensing properties is reported. The films were very sensitive to low levels of CO at elevated temperatures (200 to 400°C), although a significant cross-sensitivity to relative humidity was found. Response and recovery times were very short in comparison with a Pt-doped thick film SnO 2 pellet. The optimum working temperature was found to be 300 to 350°C, where linear responses to CO concentration and to relative humidity were seen once drift had been taken into account. All MOCVD films tested showed superior responses to a sputtered film.

Alternative precursor systems for the MOCVD of aluminium nitride and gallium nitride

Two alternative precursor systems have been investigated for the growth of AlN and GaN by MOCVD. The first involved the reaction between Me3M (M(DOUBLE BOND)Al, Ga) and tert-butylamine (tBuNH2), whilst the second route involved the pyrolysis of single-source precursors such as Me3M(NH3) (M(DOUBLE BOND)Al, Ga) and [Me2Ga(NH2)]3. Both routes proved suitable for the deposition of AlN thin films, and epitaxial AlN layers have been deposited on sapphire (0001) from Me3Al(NH3) without any added NH3. Attempts to grow GaN from Me3Ga/tBuNH2 mixtures or Me3Ga(NH3) were unsuccessful, leading to the deposition of Ga droplets, although GaN films containing a large excess of Ga were deposited by low-pressure MOCVD from the single-source precursor [Me2Ga(NH2)]3.

Investigations into the growth of AIN by MOCVD using tri-tert butylaluminium as an alternative aluminium source

Thin films of AIN have been deposited at 500 and 600 °C by atmospheric-pressure MOCVD using the precursors tri-tert-butylaluminium (But3Al) and tert-butylamine (ButNH2). Growth rates of 0.5 µm h–1 were obtained at 500 °C. Post-growth oxidation of the AIN films was prevented by the deposition of a protective Al overlayer using But3Al.

Investigations into the growth of AIN by MOCVD using trimethylsilylazide as nitrogen source

Thin films of AIN have been deposited by atmospheric-pressure MOCVD using trimethylaluminium (Me3Al) and trimethylsilylazide (Me3SiN3) as precursors. The films were deposited at 300 or 450 °C and had growth rates of up to 3 µm h–1