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Advanced Materials Research Laboratory (A.M.R.L.)

Dr. Andy Wright

Areas of research Facilities Publications Consultancy

Current research opportunities in AMRL

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OBJECTIVES

The Advanced Materials Research Laboratory (AMRL) was established in 1992 as a center for both fundamental and applied research in novel materials at Glyndŵr University in Wrexham. Previous research activities had concentrated on the growth of both conventional (ZnSe, ZnS) and novel (Ga₂Se₃, CdMgS) wide band-gap compound semiconductor materials as thin films using the technique of metal-organic chemical vapour deposition (MOCVD) for blue-green optoelectronics. Currently, a major focus of activity in the group is the broad but rapidly expanding area of Nanotechnology with particular emphasis on carbon nanotubes
.
The laboratory completed a Knowledge Transfer Partnership (KTP) project (KTP-online) with Micro Materials Ltd (Wrexham) to develop both high temperature and cold stages for their NanoTest instrument.

CURRENT AREAS OF RESEARCH

The main areas of active in-house research are in the growth of carbon nanotubes and in modelling CVD processes.

EPSRC has funded (March 2000) a project (GR/N11186) to undertake a fundamental study of the growth of carbon nanotubes by CVD. The project is based around our unique joint CVD-to-STM system as described here The project also used high resolution TEM and micro-RAMAN (with Prof.Young, Manchester Materials Centre) to gain a far better understanding of how carbon nanotubes grow from nano-sized transition metal clusters (Fe, Ni, Co or Mo) deposited onto planar substrates. The results of the initial study can be found in our publications section. Current activity has now moved from research into a proof-of-concept stage under the WDA Knowledge Exploutation Fund (KEF) programme. See the Nanotube site to get a broader overview of this area of research.

The Nanotube Site

Chemical Vapour Deposition (CVD) is widely used to synthesise thin solid films of advanced materials but is not well understood at the fundamental level. The chemistry is complex as both gas-phase and surface driven reactions can occur simultaneously. The high ambient gas pressure precludes the use of electron spectroscopies for performing experimental studies and although optical probes such as RAS (Reflectance Anisotropy Spectroscopy) can monitor the surface in real time, the only way to understand CVD on a molecular level is through high level modelling and simulation. First-principles (ab-initio) techniques have been used such as Gaussian together with Monte-Carlo modelling to perform studies of the growth processes of compound semiconductors.

EPSRC has, under its Electronic Materials for Displays (EMD) Initiative, also funded a project (GR/N28009) to develop Gallium Nitride (GaN) as a powder phosphor for Electroluminescent (EL) flexible flat-panel displays. This material is expected to yeild far longer device lifetimes than the currently used ZnS phosphors. Rare-earth doping will be used to gain superior colour purity over the use of alloys. The project is in collaboration with PACEL who manufacture these devices for the automotive and instrumentation markets.

Collaborations with other organisations include Manchester University include the TEM studies of rare-earths in both GaAs and Si/SiGe (Dept. EE&E), microwave ceramics (Materials Science Centre), High Modulus PBO fibres (Materials Science Centre) and with Coventry University the study of ACEL ZnS:Cu,Cl powder phosphors (Centre for Data Storage Materials). We also have a collaboration with the European Space Agency (Noordwijk) on the development of superconductive tunnelling junction photon detectors for astronomy (S-CAM project) where structural diagnostics are provided by us using TEM.

FACILITIES

In addition to the STM-CVD system , the facility consists of a suite of laboratories for wafer preparation, MOCVD growth and thin film characterisation. A wide variety of analytical methods are either in use or available including:

In-situ gas analysis techniques (RGA)

In-situ optical probe techniques (RAS)

Electron microscopy

Atomic Force Microscopy (AFM) -Veeco 'Explorer' AFM capable of nanolithography

Optical (low temperature (10K) photoluminescence)

Vacuum coating via an Edwards E306 evaporator enables metallisation for simple devices

Sputter coating up to 2” wafers with heated wafer stage.

Optical microscopy consists of a Reicher Polyvar Met fitted with a Normarski attachment, Olympus Vanox-T for transmission with polarised light, Olympus Stereozoom, Leitz 20EB with fluorescence and phase contast.

More recent additions to the equipment base have included a Avantes spectrometer for absolute irradiance measurements in the visible spectrum fibre-optically coupled to a monochromated high pressure mercury lamp for UV excitation

Controlled atmosphere tube furnace (1200 C max) with a silica glass flow tube capable of nitridation in high purity ammonia or annealing under high purity hydrogen or nitrogen gases. This system can also be used for wafer oxidation using pure O₂ or forming gas (H₂/N₂ mixtures) for ohmic contact formation.

Electroplating and anodising at controlled temperature.

A major part of the facility consists of an extensive suite of equipment for TEM specimen preparation and also hardware/software for image analysis & simulation. TEM is used with cross-sectional specimens to obtain information on the interfaces and surface profiles of epitaxial layers via access to the TEM and STEM instruments in Manchester and Liverpool. Image analysis/processing (SEMPER) and HRTEM image simulation (EMS and Cerius2) are used as routine tools for interpretation of image data.

Services to industry

We are able to undertake cutting, drilling and polishing of hard materials such as ceramics, semiconductors and glasses and have recently done work for BAE Systems. Vacuum coating with controlled thickness of films is also offered. Follow this link for more details of facilities and capabilities.

SELECTED PUBLICATIONS

Nanotubes
Chemical Vapour Deposition
Microscopy of Materials
Modelling of CVD

Carbon Nanotubes

The influence of the substrate on the growth of carbon nanotubes from nickel clusters -an investigation using STM, FE-SEM, TEM and Raman spectroscopy
A C Wright, Y Xiong, N Maung, S J Eichhorn and R J Young
Materials Scince and Engineering C 23 (2003) 279-283 (PDF)

CVD growth of semiconductors

High resolution and conventional transmission electron microscopy of Ga₂Se₃ thin films grown by vapour phase epitaxy
A C Wright and J O Williams, A Krost, W Richter and D R T Zahn
J. Crystal Growth 121 (1992) No's 1/2 111

Mass-spectrometric study of the pyrolysis reactions in the movpe of Ga₂Se₃ by in-situ gas sampling
N Maung, G H Fan, T L Ng, J O Williams and A C Wright
Journal of Crystal Growth, (1996), 158, no.1-2, 68-78

Homogeneous thermal-decomposition of dimethylzinc in a metal-organic
vapor-phase epitaxy reactor - an ex-situ investigation by FTIR absorption-spectroscopy
G H Fan , N Maung, T L Ng, J O Williams and A C Wright
Journal of the Chemical Society -Faraday Transactions, (1995), 91, No.19, 3475-3479

Metal-Organic Vapour Phase Epitaxial Growth of Cubic Gallium Selenide, Ga₂Se₃
T L Ng, N Maung, G Fan, I B Poole, J O Williams, A C Wright, D F Foster and D J Cole-Hamilton
Chemical Vapour Deposition (1996) 2, number 5, 185-189

Thermal decomposition of D^tBuSe and DMZn in an MOVPE reactor system
G H Fan, N Maung, T L Ng, P F Heelis, J O Williams, A C Wright, D F Foster and D J Cole-Hamilton
J. Crystal Growth. 1997, 170, No.1-4, 485-490.
Presented at ICMOVPE VIII, Cardiff, 1996

Growth studies by Reflectance Anisotropy Spectroscopy (RAS) on MOVPE grown ZnSe
D Gnoth, I B Poole, T L Ng, D A Evans, N Maung, J O Williams and A C Wright
J. Crystal Growth. 1997, 170, No.1-4, 198-202.
Presented at ICMOVPE VIII, Cardiff, (1996)

MOVPE growth of Magnesium Cadmium Sulphide: Rocksalt of Sphalerite?
I B Poole, T L Ng, N Maung, J O Williams and A C Wright
J. Crystal Growth. 1997, 170, No.1-4, 528-532.
Presented at ICMOVPE VIII, Cardiff, (1996)

Metal-Organic Chemical Vapour Deposition for the preparation of new materials and interfaces
J O Williams, N Maung and A C Wright
Chapter 11 from 'Interfacial Science'. A 'Chemistry for the 21st Century' monograph. Blackwell Science.

Dynamic vapour pressure measurements of di-tertiarybutyl sulphide using an ultrasonic monitor
L D Stockton , T L Ng, N Maung, I B Poole, J O Williams, A C Wright, D F Foster, D J Cole-Hamilton
Journal of Crystal Growth, (1998), 183, No.1-2, pp.95-98

Growth of MgS by MOVPE: The Choice of Sulphur Precursor
L. D. Stockton, T. L. Ng, N. Maung and A C Wright
J. Mater. Sci: Materials in Electronics, (1998), 9, Number 3, pp.207-210

Direct synthesis of II₃-V₂ compound semiconductors by the Heterovalent Exchange Mechanism
A C Wright, T L Ng and N Maung
Philos. Mag. Vol. A79, No.11 (1999) 2691-2710

A study of the mechanism of the reaction of trimethylgallium with hydrogen selenide
N Maung, G Fan, T-L Ng, J O Williams and A C Wright
J. Mater. Chem., (1999), 9, 2489-2494

Unusual binary optical reflectivity of highly structured epitaxial gallium selenide thin films
A C Wright, T L Ng and N Maung
Advanced Materials, 12 (2000) 273-276

Catching the action on camera to grow thin films
A C Wright, Materials World, July (1999), 409

Microscopy of materials

Detection of compound formation at the ZnSe/GaAs interface using high resolution transmission electron microscopy (HRTEM).
A C Wright and J O Williams
Journal of Crystal Growth, J Crystal Growth 114 (1991) 99-106

Growth and structural characterisation of molecular beam epitaxial erbium-doped GaAs
I Poole, K E Singer, A R Peaker and A C Wright
J. Crystal Growth 121 (1992) 121

Self-organising growth of erbium arsenide quantum dots and wires in gallium arsenide by molecular beam epitaxy
K E Singer, P Rutter, A R Peaker and A C Wright
Applied Physics Letters, 64 (1994) 707

Two beam high resolution dark-field imaging: Applications to epitaxial semiconducting materials
A C Wright and J O Williams
Proc. Conf. Microscopy of semiconducting materials (1993). Oxford University
IOP publishing. Conference series No. 134; section 1, pages 51-54

Structural characterisation of luminescent Ca_0.95Cd_0.05S
A C Wright, I V F Viney, B Ray, J Britewell and B W Arterton
J. Materials Science: Materials in Electronics 7 (1996) 305-308

Orientation dependent growth of TmAs wires in GaAs grown by MBE
A C Wright, M R Bennett and K E Singer
Proc. conf. Microscopy of semiconducting materials -10 (1997). Oxford University 7-10 April
IOP publishing, Bristol. Conference series No. 157 ; section , page 385-388.

MOVPE Growth of ZnSe: The effect of initiation conditions -a study by TEM
A C Wright, D N Gnoth, T L Ng and N Maung.
Applied Surface Science. Volumes 123/124 (1998) 555-559

Microstructure of Zinc Selenide single crystals grown by Solid Phase Recrystallisation
A C Wright
J. Crystal Growth, Vol. 203 No. 3 (1999) 309-316

Artefacts in Iodine-Ion milling of some compound semiconductors
A C Wright
Ultramicroscopy, Vol. 83 (2000) 1-8

A structural evaluation of ZnS-based electroluminescent phosphors and devices: a comparison with performance
A C Wright and I V F Viney
Philos. Mag. B, Vol. 81 No. 3, (2001), 279-297

On the origin of compositional fluctuations in ZnSe1-xSx alloys grown by metal-organic vapour phase epitaxy
A C Wright and N Maung
Philos. Mag. Vol. 83 No. 22, (2003) 2641-2652 (PDF)

Two-component dendritic gels: Easily tunable materials
A R Hirst, D K Smith, M C Feiters, H P M Geurts and A C Wright
J. AMERICAN CHEM. SOC. Vol. 125 (30) (2003) 9010-9011 (doc). Supplementary material (doc)

Oligomerisation and neurotoxicity of the amyloid ADan peptide implicated in Familial Danish Dementia
V Lelyveld, N Gunasekera, M Lee, G Gibson, O M A El-Agnaf, A C Wright and B Austen. J. Neurochemistry 88(2) (2004) 281-290 (doc).

Modelling of CVD

An Ab Initio and Density Functional Theory Study of the Trimethylgallium- Hydrogen Selenide Adduct: (CH₃)₃Ga:SeH₂,
N Maung, Journal of Molecular Structure (THEOCHEM), (1998), 432, 129-137

An Ab Initio and Density Functional Theory Study of the Dimethylzinc- Hydrogen Selenide Adduct: (CH₃)₂Zn:SeH₂,
N Maung, Journal of Molecular Structure (THEOCHEM), (1998), 434, 255-264

The evaluation of bond dissociation energies for simple sulphur containing molecules using ab initio and density functional methods
N Maung, Journal of Molecular Structure (THEOCHEM), (1999), 460, No.1-3, pp.159-166

Studies of the thermal and photochemical decomposition mechanisms of Bu^t₂Se in the presence of Me₂Zn using deuterium labelled analogues
N L Pickett, D L Foster, N Maung and D J Cole-Hamilton
J. Materials Chemistry, 9 (1999) 3005-3014

CONTACT
Dr. A. C. Wright,
PP19, Faculty of Science and Technology
Glyndŵr University,
Plas Coch, Mold Road,
Wrexham,
LL11 2AW,
U.K.

Tel. 01978 293369 (+44 1978 293369)
Fax 01978 290008 (+44 1978 290008)
Email:

The pages on this site are maintained by -Andy Wright- and were last modified on 28th October 2008

Copyright exist on all material on this site. Copyrighted material is provided for research and private use only and may only be copied or used for other purposes with permission.

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