Dr Richard Cross

Job: Senior Research Fellow

Faculty: Technology

School/department: School of Engineering and Sustainable Development

Research group(s): Emerging Technologies Research Centre (EMTERC)

Address: De Montfort University, The Gateway, Leicester, LE1 9BH, United Kingdom

T: +44 (0)116 250 6157

E: rcross@dmu.ac.uk

W: https://www.dmu.ac.uk/emterc

 

Personal profile

Most of my research career has been focused on the growth of thin films for electronic devices such as thin film transistors (TFTs); mainly hydrogenated amorphous silicon and zinc oxide. My main interests now lie in the novel growth of nanoscale materials. Of particular interest going forward will be exploring the nano-bio interface, i.e. interfacing directly nanoscale materials/devices with biological systems. Examples would be neuronal interfaces and structures for intracellular recording/biomarker detection.

Research group affiliations

Emerging Technologies Research Centre (EMTERC)

Publications and outputs 

  • Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics
    Electrical Performance and Stability of ZnO Thin-Film Transistors Incorporating Gadolinium Oxide High-k Dielectrics Ngwashi, Divine K.; Paul, Shashi; Devi, Anjana; Cross, R. B. M. This work investigates the performance and gate bias stress instability of ZnO-based thin film transistors (ZnO-TFTs) incorporating amorphous gadolinium oxide, a high-k dielectric material. ZnO thin films produced via radio frequency (RF) reactive magnetron sputtering were used as channel layers. The source/drain electrodes were achieved by the thermal evaporation of aluminium on a bottom gate inverted staggered ZnO TFT structure. Gadolinium oxide (Gd2O3) deposited by metal-organic chemical vapour deposition (MOCVD) served as the gate dielectric. The electrical characterisation of the ZnO-TFTs produced showed improvement in performance and stability in comparison to thermally-grown SiO2-based ZnO TFTs fabricated under the same conditions. The effective channel mobility, on-off current ratio and subthreshold swing of the TFTs incorporating Gd2O3 dielectric were found to be 33.5 cm2 V-1s-1, 107, and 2.4 V/dec respectively when produced. The electrical characterisation of the same devices produced with SiO2 dielectrics exhibited effective mobility, on-off current ratio and subthreshold swing of 7.0 cm2 V-1s-1, 106 and 1.4 V/dec respectively. It is worth noting that, the ZnO active layer was sputtered under room temperature with no intentional heating and post-deposition annealing treatment. On application of gate bias stressing on these thin film transistors, it was observed that threshold voltage instability increased with stress period in all device types. Transistors incorporating Gd2O3 however, were found to exhibit lesser threshold voltage related instability with regards to gate bias stressing in comparison to similar devices incorporating SiO2 as gate dielectric. It was also observed that the effective mobility in both devices tend to stabilize with prolonged gate bias application. In this work, it is demonstrated that Gd2O3 dielectric is a potential alternative to SiO2 for the fabrication of ZnO TFTs with improved performance and electrical stability under prolonged use. open access article
  • A multi-faceted approach to determining the efficacy of metal and metal oxide nanoparticles against bacterial biofilms
    A multi-faceted approach to determining the efficacy of metal and metal oxide nanoparticles against bacterial biofilms Tejpal, Jyoti; Cross, R. B. M.; Owen, Lucy; Paul, Shashi; Jenkins, R. O.; Armitage, David; Laird, Katie Antibacterial efficacy of nanoscale silver, copper (II) oxide and zinc oxide were assessed against Pseudomonas aeruginosa and Staphylococcus aureus biofilms in solution and on surfaces. Using a Center for Disease Control biofilm reactor, minimum biofilm reduction concentrations, the coefficient of determination (R2) and log(10) reductions were determined. Atomic absorption spectroscopy, scanning electron microscopy and confocal laser scanning microscopy were used to assess the disruption of the biofilms. The efficacy of thin films of zinc oxide and silver deposited via magnetron sputtering and thermal evaporation respectively was also assessed. Minimum biofilm reduction concentrations of zinc oxide or silver nanoparticles were 256 or 50 µg/ml for P. aeruginosa and 16 or50 µg/ml for S. aureus respectively. When tested in combination the nanoparticles concentrations were at least halved resulting in significant (p ≤0.05) biofilm reductions of 3.77 log(10) - 3.91 log(10). Biofilm growth on thin films resulted in reductions of up to 1.82 log(10). The results suggest that nanoparticle suspensions and thin films of zinc oxide and may have potential as antimicrobial treatments for hard to eliminate biofilms in a clinical environment.
  • Nitridation of optimised TiO⁠2 nanorods through PECVD towards neural electrode application
    Nitridation of optimised TiO⁠2 nanorods through PECVD towards neural electrode application Sait, R. A.; Govindarajan, S.; Cross, R. B. M. A neural electrode interface material is a key component for effective stimulation and recording of neuralactivity. The fundamental requirement of a neural electrode is for it to be able to deliver adequate charge to targeted neuronal population. Coating electrode surfaces with nanostructured material not only provides an increase in surface area, providing relatively more active sites for charge delivery than planar systems, but also allows for the reduction of electrode dimension to reduce invasiveness and increase selectivity. In this work, titanium nitride nanowires (TiN-NWs) synthesised by novel nitridation process in Plasma Enhanced Chemical Vapour Deposition (PECVD) is suggested as an enhanced coating material for neural electrodes. The synthesis involved the solution growth of crystalline titanium oxide nanorods (TiO⁠2-NRs) from a sputtered TiN nucleation layer followed by nitridation. TiO⁠2-NRs exhibited high aspect ratio of 23.1 and were converted into TiN after one hour of nitridation at 600°C. Evidence of conversion was studied by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). The nitridation temperature and time reported here are the lowest and shortest as compared to the literature. The near-stoichiometric TiN-NWs (x=0.49) achieved in this work were used subsequently for electrochemical characterisation through Cyclic Voltammetry (CV). The capacitance of relatively high aspect TiN-NWs was 3.78mF/cm⁠2⁠, which was a 5-fold enhancement compared to thin film of TiN layer (0.7 mF/cm⁠2). A stability test of the nanowires were performed in which the capacitance remained relatively unchanged. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Design and characterization of a diamond-shaped monopole antenna
    Design and characterization of a diamond-shaped monopole antenna Maricar, Mohamed Ismaeel; Bahar, A.; Greedy, S.; Phang, S.; Gradoni, G.; Cross, R. B. M.; Creagh, S.; Tanner, G.; Thomas, D. W. P. The resonant frequency of a diamond shaped monopole antennas is analysed by using a finite difference time domain method. The diamond shaped monopole antennas was fabricated and tested experimentally on RT Duroid material and then the results were directly compared with simple monopole antennas., Tthe work shows that the diamond shaped monopole antennas has smaller dimensions, higher bandwidth and gain at millimeteric wave frequency . Experimentally measured diamond shaped monopole antennas has good agreement with simulated results. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Facile Preparation of Drug-Loaded Tristearin Encapsulated Superparamagnetic Iron Oxide Nanoparticles Using Coaxial Electrospray Processing
    Facile Preparation of Drug-Loaded Tristearin Encapsulated Superparamagnetic Iron Oxide Nanoparticles Using Coaxial Electrospray Processing Rasekh, M.; Ahmad, Z.; Cross, R. B. M.; Hernandez-Gil, Javier; Wilton-Ely, James D. E. T.; Miller, Philip W. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Synthesis and characterization of sputtered titanium nitride as a nucleation layer for novel neural electrode coatings
    Synthesis and characterization of sputtered titanium nitride as a nucleation layer for novel neural electrode coatings Sait, R. A.; Cross, R. B. M. A growing demand for chronically implantable electrodes has led to a search for the most suitable neural electrode interface material. Nobel metals such as Platinum (Pt) are inadequate for electrode/neuron interfaces at small scales due to their poor electrochemical properties, low charge injection and high charge density per unit area. Titanium Nitride (TiN) has been implemented in neural electrodes application due to its outstanding properties. In this work, TiNx films were deposited by non-reactive Radio Frequency (RF) magnetron sputtering towards the development of a novel TiN nanowires (NWs) neural interface. Although, there is substantial work on this material, its growth using non- reactive RF magnetron sputtering has not been reported previously and optimised towards the growth of TiN NWs and their use in neural interface applications. The sputtering parameters of RF power and Argon (Ar) flow rate were varied in order to investigate their effects on the structural, electrical and electrochemical properties of the TiN films. A dense film morphology was observed in the Scanning Electron Microscopy (SEM) images of TiN thin films showing a columnar structure. The film preferential orientation was changed between (200) and (111) with Ar flow rate due to the variation of the kinetic energy (KE) of the sputtered atoms. The crystallites size obtained were in the range of 13 to 95 nm. Surface roughness was found to increase from 0.69 to 1.95 nm as Ar flow rate increased. TiNx films showed a good electrical resistivity of 216 µΩ.cm. Stoichiometry was found to vary with sputtering conditions in which the nitrogen content was found to deplete from the film at low Ar flow rate. The electrochemical behaviour of TiN films was characterised and the highest capacitance value obtained was 0.146 mF/cm^2 The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Shape-dependent antibacterial activity of silver nanoparticles on Escherichia.coli and Enterococcus.faecium bacterium
    Shape-dependent antibacterial activity of silver nanoparticles on Escherichia.coli and Enterococcus.faecium bacterium Alshareef, A.; Laird, Katie; Cross, R. B. M. Silver nanoparticles (AgNPs) have been shown to exhibit strong antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria including antibiotic resistant strains. The antibacterial activity of AgNPs against Escherichia coli and Streptococcus mutans (S. Mutans) has been reported and found to be size dependent. This study aims to compare the bactericidal effect of different shaped AgNPs (spherical and truncated octahedral) against E.coli and E.faecium. The antimicrobial activity of a range of concentrations (50, 100, 1000μg/ml) was determined over 24 hours using both optical density and viable counts. Truncated octahedral AgNPs (AgNoct) were found to be more active when compared with spherical AgNPs (AgNS). The difference in shape resulted in differences in efficacy which may be due to the higher surface area of AgNOct compared to AgNS, and differences in active facets and surface energies, with AgNPs having a bacteriostatic effect and AgNOct is being bactericidal after 4 hours. The results suggest that AgNPs can be used as effective growth inhibitors in different microorganisms, rendering them applicable tovarious medical devices and antimicrobial control systems. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Chemical Synthesis of Copper Nanospheres and Nanocubes and Their Antibacterial Activity Against Escherichia coli and Enterococcus sp.
    Chemical Synthesis of Copper Nanospheres and Nanocubes and Their Antibacterial Activity Against Escherichia coli and Enterococcus sp. Alshareef, A.; Laird, Katie; Cross, R. B. M. The interest in synthesising inorganic nanomaterials for biological applications has increased in recent years, especially for antibacterial purposes. In the present study, spherical and cube-shaped copper nanoparticles were synthesised by a chemical reduction method and their efficacy as antimicrobial agents against both Gram-negative (Escherichia coli) and Gram-positive (Enterococcus sp.) organisms investigated. The nanoparticles were characterised using ultraviolet/visible spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction. Copper nanocubes were found to be more antimicrobial when compared with copper nanospheres, and it is postulated that whilst both sets of nanoparticles have similar total surface areas, the different shapes have different active facets and surface energies, which may lead to differing bactericidal behaviour. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. The fulltext can also be viewed at this link: http://rdcu.be/mVXD
  • Preliminary Design and Characterisation of a Novel T-shaped Nanoantenna on Diamon Like Carbon Material
    Preliminary Design and Characterisation of a Novel T-shaped Nanoantenna on Diamon Like Carbon Material Bahar, A.; Maricar, Mohamed Ismaeel; Cross, R. B. M.
  • DSP Control of Smart Antennas
    DSP Control of Smart Antennas Maricar, M.; Bahar, A.; Raju, Y.; Glover, James; Nama, K.; Cross, R. B. M. Modern beam steered antennas where pattern is shaped according to optimum criteria. Smart antennas are the practical realization of adaptive array signal processing. Smart antennas can be applied to mobile wireless communication, WLAN, Wi-Max, MANET, MIMO systems; satellite communication etc. In mobile wireless communication smart antenna can provide higher system capacity by directing narrow beams towards users of interest. Smart antennas mitigate the effects multi-path fading. Smart antennas pattern are controlled via adaptive algorithms based upon maximizing signal to interference ratio, minimizing mean square Error (MSE), steering towards signal of interest, nulling interference. A smart antenna consists of an array of antenna elements (Dipole, Microstrip etc) and uses Digital Signal Processing (DSP) for phase shifting of the signal feed to individual elements of the array. In this paper, we are going to design a DSP control smart antennas array with digital beam forming techniques. Multiple Resonant is achieved by changing the structure of normal patch antenna. These antennas will be suitable for mobile and wireless LAN communication Centre for Electronic and Communications Engineering

Click here to view a full listing of Richard Cross' publications and outputs.

Research interests/expertise

Nanoscale materials (nanowires, nanotubes) for health applications

Exploring the nano-bio interface

Large area electronic materials

Thin films

TFTs

Areas of teaching

Analysis of micro and nanoscale materials

Growth/deposition of electronic materials

Fabrication of micro and nanoelectronic devices

Qualifications

BSc

MSc

PhD

Courses taught

Electrical and Physical Measurements (ENGT5129)

Fabrication Technologies (ENGT5127)

Membership of professional associations and societies

01/09-date: Material Research Society (full member)

Projects

RIF project: A Cleaner, Greener, Low Carbon Fabrication Process for Photovoltaic (PV) Solar Cells
Start Date: 01/04/10
End Date: 01/07/10
Role: Co-Worker
PI: Shashi Paul
Project Aims:
• To demonstrate, for the first time, a photovoltaic solar cell using a novel low temperature, high growth rate, and low-cost process (developed within EMTERC) based on thin films of silicon.
• Approach industries with a view to the commercialisation of the technology.
• To develop new and enhance existing collaborative links with major players in the field of PV both in the UK and Europe.

RIF project: Enhancing IR Micro Sensor Technology To More Accurately Measure the Temperature Profile of Electronic Devices
Start Date: 01/04/10
End Date: 01/07/10
Role: Co-Worker
PI: Chris Oxley
Project Aims:
• The objective of the work was to explore the feasibility of moving controllably a single characterised IR micro sensor in micron steps along the channel of a GaN transistor to measure more accurately the temperature profile of the channel region of the device.

Consultancy work

Area of expertise: Analysis of micro/nano materials

Previous consultancies: Analysis of optical coating for CVI Melles Grigot

Currently available: Yes

Current research students

Second supervisor for:

Keith McGrath
Sultan Alotaibi
Faleh Alotaibi

Professional esteem indicators

Reviewer for:

Applied Physics Letters
AIP Advances
Journal of Applied Physics
IEEE Transactions on Electron Devices
IEEE Electron Device Letters
IEEE Micro and Nano Letters
Journal of Physical Chemistry
Journal of the Electrochemical Society
Solid State Communications
Solid State Electronics
Materials Science and Engineering B
Electrochemical and Solid State Letters
Electronics and Telecommunications Research Institute Journal
Journal of Vacuum Science and Technology A

RichardCross1

Search Who's Who

 

 
News target area image
News

DMU is a dynamic university, read about what we have been up to in our latest news section.

Events target area image
Events

At DMU there is always something to do or see, check out our events for yourself.

Mission and vision target area image
Mission and vision

Read about our mission and vision and how these create a supportive and exciting learning environment.