Thin transparent conducting oxide (TCO) films of gallium-doped zinc oxide have been deposited on glass substrates by atomic layer deposition (ALD) using diethyl zinc, triethyl gallium and water vapour as precursors. The gallium-doped zinc oxide films were deposited over the temperature range 100-350°C. Transmission electron microscopy reveals that the as-deposited films are polycrystalline in character. The electrical resistivity of the gallium-doped zinc oxide films was evaluated using four-point probe and contactless measurement methods as a function of film thickness. The lowest sheet resistance of 16 Ω/☐ was measured from a film thickness of 400nm and a gallium content of 5 atomic percent. The electron Hall mobility of this film was 12.3 cm2/Vs. The visible transmittance of the films was 78% with a haze of 0.2%.

Quantitative analysis of the elemental distributions within AlGaN has been investigated using electron energy loss spectroscopy in a scanning transmission electron microscopy. The nanowires were grown on c-sapphire by radio frequency plasma assisted molecular beam epitaxy. Crystallographic and compositional analyses of the nickel seeds used to promote the nanowire type growth yielded values of lattice spacings within the seeds remaining at the growth tip which were attributed to either (002) NiO, (111) Ni3Ga or (111) Ni-Ga solid solution. The seeds structures exhibited a metallic core encompassed by an oxide shell. The relative gallium and nickel concentrations were quantified by EELS analyses and were found to be consistent with the equilibrium phase α' of Ni3Ga or Ni-Ga solid solution. No nitrogen was observed within the seeds, which is predicted thermodynamically due to the instability of Ni-N compounds at the NW growth temperature used in this study. No aluminium was detected at the tip of nanowires. These measurements are compared with previous studies made concerning pure GaN nanowires. The Al distribution along the nanowire length was measured and is discussed in respect of a possible Al incorporation mechanism.

The synthesis of SrBi2Ta2O9 (SBT) thin films has been investigated using a superlattice approach. Thin films were deposited on silicon by independent injection of each source to produce Bi2O3/SrTa2O6 superlattices. The effects of post-deposition annealing have been investigated using high-resolution TEM and medium energy ion scattering (MEIS) to depth profile the superlattices. X-ray diffraction has also been used to characterize the conversion of the superlattices from distinct layers of Bi2O3 and SrTa2O6 into a polycrystalline layer of strontium bismuth tantalate.

Epitaxial ScxGa1-xN films of low Sc concentration (x = 0.08 ± 0.01) were deposited on MOCVD-grown GaN films (using an Al2O3 substrate) at 800°C using molecular beam epitaxy employing ammonia as a reactive nitrogen source (NH3-MBE). The strain-free lattice parameters of the films were determined using a method based on high-resolution X-ray diffraction (HRXRD) in conjunction with an in-situ elastic tester. It is found that the c:a lattice parameter ratio increases slightly and that the Poisson’s ratio decreases with increasing Sc concentration. The crystalline quality and long-range ordering of the ScxGa1-xN films (as indicated by HRXRD peak intensities and full width at half maximum values) is improved considerably relative to the GaN template. Our results indicate that threading dislocations do not propagate effectively into the ScxGa1-xN films and that these may therefore potentially find application as dislocation blocking layers in GaN-based optoelectronic devices.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

A range of “single source” Sr-Nb and Sr-Ta heterometal alkoxides precursors are investigated as potential sources for liquid injection MOCVD (metalorganic chemical vapour deposition) and ALD (atomic layer deposition) of SrBi2Ta2O9 (SBT) and SrBi2(TxNb1-x)2O9 (SBTN). These “single source” precursors are designed to alleviate the mis-match between conventional Sr and Ta or Sr and Nb sources. Strontium-tantalate and strontium-niobate thin films were deposited on silicon using the “single source” alkoxide precursors [Sr{Ta(OEt)5(dmae}2] and [Sr{Nb(OEt)5(dmae)}2] (dmae = OCH2CH2NMe2), and the optimum temperatures for deposition of stoichiometric SrTa2O6 and SrNb2O6 were determined. Separate ALD studies of [Sr{Ta(OEt)5(dmae)}2] and [Sr{Ta(OEt)5(mee)}2] (mee = OCH2CH2OMe) for the growth of strontium-tantalate were carried out to assess precursor suitability for this technique. Liquid injection MOCVD of Bi-oxide films using Bi(mmp)3 indicates similar decomposition behaviour to the Sr-Ta and Sr-Nb alkoxides, demonstrating its suitability as a complementary source of Bi for SBT, SBN and SBTN.

High purity lanthanum oxide and praseodymium oxide thin films (C< 1 at.-%) have been deposited by liquid injection MOCVD using the volatile alkoxide precursos [La(mmp)3] and [Pr(mmp)3] in toluene-solution (mmp = OCMe2CH2OMe). 1H NMR solution studies have shown that the addition of donor species, such as tetraglyme (CH3O(CH2CH2O)4CH3) or mmpH prevent molecular aggregation and help stabilise the precursors.

High purity lanthanum oxide and praseodymium oxide thin films (C< 1 at.-%) have been deposited by liquid injection MOCVD using the volatile alkoxide precursos [La(mmp)3] and [Pr(mmp)3] in toluene-solution (mmp = OCMe2CH2OMe). 1H NMR solution studies have shown that the addition of donor species, such as tetraglyme (CH3O(CH2CH2O)4CH3) or mmpH prevent molecular aggregation and help stabilise the precursors.

Bismuth titanate thin films have been grown by liquid injection MOCVD using Bi(mmp)3 in combination with the new Ti precursors Ti(OPri)2(mmp)2 and Ti(mmp)4 (mmp = OCMe2CH2OMe). Films were grown on Si(100) substrates over the temperature range 300 – 600°C, and were shown to consist predominantly of the Bi4Ti3O12 phase at substrate temperatures > 500°C.

The alkoxide and alkylamide complexes [Hf(mmp)4] and [Hf(NMe2)4] 2 are both promising precursors for the MOCVD of HfO2. A comparison has shown that [Hf(NMe2)4] 2 deposits oxide at lower temperatures and over a wider temperature range then [Hf(mmp)4].

Both passive and active electronic applications of CVD diamond have been proposed since the earliest stages of its development, largely based on an extrapolation of the superlative properties of single crystal diamond. Consequently, CVD diamond research has striven hard to match up to this expectation and significant advances have been made.

CVD diamond compares favourably with natural or high pressure synthetic single crystal material for passive electronic applications. The development of CVD diamond deposition technology for thermal management has led producers to address issues such as production cost, yield and quality. CVD polycrystalline diamond is becoming a commodity material and commercial applications in thermal management are emerging. Many of these developments are expected to feed into active electronic applications and will act as a springboard for diamond into commercial technology.

The active electronic applications for diamond are more demanding in terms of materials and process technologies. For example, doping, structure delineation and contact schemes have been widely demonstrated and prototype devices are showing potential benefits in sensors, detectors, photonics and cold cathodes. The current and future status of diamond electronics is reviewed.