Simon A. Rushworth

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.

Recent developments in metalorganic precursors for metalorganic chemical vapour deposition

Abstract Volatile metalorganic compounds are finding an increasing application in the deposition of metals and semiconductors by metalorganic chemical vapour deposition (MOCVD). In this paper, the use of some new precursor systems in the growth of selected metals and alloys is reviewed with emphasis being placed on precursor chemistry in the gas phase and at the growth surface.

Growth of aluminium films by low pressure chemical vapour deposition using tritertiarybutylaluminium

The new aluminium precursor, tritertiarybutylaluminium (TTBA), has been used successfully for the growth of high purity aluminium films by low pressure chemical vapour deposition (LPCVD). The aluminium films were grown over the temperature range 300–450°C on Si(111) substrates and had growth rates of up to 2 μm min-1. A comparison with aluminium films grown using triisobutylaluminium (TIBA) is made.

Liquid injection atomic layer deposition of silver nanoparticles

Silver nanoparticles are being developed for applications in plasmonics, catalysts and analytical methods, amongst others. Herein, we demonstrate the growth of silver nanoparticles using an atomic layer deposition (ALD) process for the first time. The silver was deposited from pulses of the organometallic precursor (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) dissolved in a 0.1 M toluene solution. Catalytic oxidative dehydrogenation of the silver was achieved using intermittent pulses of propanol. The effect of substrate temperature on the size and distribution of nanoparticles has been investigated over the temperature range 110-150 degrees C. Transmission electron microscopy reveals that the nanoparticles consist of face centred cubic, facetted silver crystallites. The localized surface plasmon modes of the nanoparticles have been investigated using electron energy loss spectroscopy mapping. The distributions of plasmons within the ALD nanoparticles are comparable to those grown by solution methods. Both dipolar and quadrupolar resonant modes are observed, which is consistent with previous discrete dipole approximation models. Energy loss mapping of a loss feature at 8.1 eV reveals that it correlates with the bulk or volume region of the silver nanoparticles investigated here.

Addition of yttrium into HfO2 films: Microstructure and electrical properties

The cubic phase of HfO2 was stabilized by addition of yttrium in thin films grown on Si∕SiO2 by metal-organic chemical vapor deposition. The cubic phase was obtained for contents of 6.5at.% Y or higher at a temperature as low as 470°C. The complete compositional range (from 1.5to99.5at.% Y) was investigated. The crystalline structure of HfO2 was determined from x-ray diffraction, electron diffraction, and attenuated total-reflection infrared spectroscopy. For cubic films, the continuous increase in the lattice parameter indicates the formation of a solid-solution HfO2–Y2O3. As shown by x-ray photoelectron spectroscopy, yttrium silicate is formed at the interface with silicon; the interfacial layer thickness increases with increasing yttrium content and increasing film thickness. The dependence of the intrinsic relative permittivity er as a function of Y content was determined. It exhibits a maximum of ∼30 for ∼8.8at.% Y. The cubic phase is stable upon postdeposition high-temperature annealing at 900°C und...

MOVPE growth of AlGaAs using trimethylamine alane

Abstract Single layers of AlGaAs and quantum wells of GaAs/AlGaAs have been grown from the adduct trimethylamine alane (NMe 3 ·AlH 3 ), trimethylgallium (TMG) and arsine (AsH 3 ) using atmospheric pressure MOVPE. The growth is characterised by rapid darkening of the reactor due to a homogeneous side reaction. Low temperature photoluminescence data from the alloy Al 0.33 Ga 0.67 As shows that there is no reduction in the residual carbon contamination compared to a similar layer deposited from trimethylaluminium, TMG and AsH 3 . The trend in electrical properties indicates an increasing acceptor concentration arising from the high purity TMG source. We have proposed that methyl groups from TMG are the precursors to the observed carbon contamination in NMe 3 ·AlH 3 grown AlGaAs.

The growth of CdS and CdSe alloys by MOCVD using a new dimethylcadmium adduct

Abstract High quality epitaxial layers of CdS and CdSe have been grown by MOCVD using a tetrahydrothiophene adduct of dimethylcadmium. Good quality layers were grown in the temperature range 300 to 500°C. Layers were grown on both (100) GaAs and (111) GaAs substrate orientation with the latter displaying the best optical properties.

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.

Atomic Layer Deposition of Hafnium Silicate Thin Films Using Tetrakis(diethylamido)hafnium and Tris(2-methyl-2-butoxy)silanol

Hafnium silicate films were grown by atomic layer deposition using the liquid precursors tetrakis(diethylamido)hafnium (TDEAH) and tris(2-methyl-2-butoxy)silanol, [CH 3 CH 2 C(CH 3 ) 2 O] 3 SiOH (TMBS). Using in situ ellipsometry, ex situ high resolution transmission electron microscopy (HRTEM), medium energy ion scattering (MEIS), and X-ray photoelectron spectroscopy (XPS), the details of the film thickness and composition were examined as functions of both the substrate temperature and silanol pulse time. Both HRTEM and MEIS measurements revealed that the films comprised two layers, with the surface layer containing more Hf than the layer in contact with the substrate. A self-limiting growth with a rate ~ 1ML/cycle was observed only after several initial cycles, a behavior that is ascribed to the chemistry of the initial Si substrate surface. Hf 4f XPS confirmed that the films were stoichiometric Hf x Si 1-x O 2 throughout despite the nonconstant Hf concentration with depth. A reaction mechanism between TDEAH and TMBS is proposed.

Metal-organic chemical vapour deposition of mixed-conducting perovskite oxide layers on monocrystalline and porous ceramic substrates

Perovskite oxide layers, i.e. manganites La1−x(Sr,Ca)xMnO3, ferrates La1−xSrxFe1−yCoyO3, gallates La1−xSrxGa1−y(Co,Ni,Fe)yO3 of a thickness of 0.8–2 μm, were deposited by pulsed injection MOCVD (metal-organic chemical vapour deposition) on various monocrystalline and porous ceramic substrates. The layers were characterised by X-ray diffraction, scanning electron microscopy, wavelength dispersion spectroscopy and by electrical measurements of the total conductivity vs. temperature. Such oxides are known as mixed electronic–ionic conductors and are largely studied as materials for the fabrication of oxygen permeable membranes. One of the aims of this work was to estimate the suitability of the pulsed injection MOCVD technique for the preparation of dense perovskite layers for their use as membranes for oxygen.