Dr. Matthew Zervos M.Zervos obtained his BEng (Honours) in Electrical and Electronic Engineering from the University of Surrey between 1987-1991 and MSc in Microelectronic Materials and Devices at the University of Manchester Institute of Science and Technology (UMIST) between 1991-1992. Completed a PhD in semiconductor physics on 'Delta–doping of InGaAs quantum wells grown by Molecular Beam Epitaxy' in the Department of Physics at the University of Wales,Cardiff between 1994-1998.
Has worked for STC Technology Ltd at Harlow in the UK and Philips Research Laboratories in Eindhoven the Netherlands, on compound semiconductors and nanotechnology but also for the University of Crete and the Foundation Of Research and Technology Hellas (FORTH) at the Institute of Electronic Structure and LASERs (IESL) in Greece.
He has a broad range of expertise covering synthesis, electrical ,structural and optical characterization of semiconductor materials, device processing including optical and electron beam lithography and computational semiconductor physics. M.Zervos joined the University in August 2006 and set up the Nanostructured Materials and Devices Laboratory in May 2008 for the growth of semiconductor nanowires and the study of their fundamental properties and energy related device applications .
He currently teaches mechatronics and control engineering as part of the undergraduate curriculum and semiconductor physics to postgraduates undertaking research in the materials science group of the department but also for postgraduates from other departments e.g. electrical engineering and physics.
Finally he is a chartered engineer (CEng) of the Institute of Electronic and Electrical Engineers (IEE) and also holds the title of chartered physicist (CPhys) of the Institute of Physics (IoP) in the UK.
Research activities are currently focused on the synthesis of n- and p-type metal oxide and sulphide semiconductor nanowires their structural, electrical and optical properties but also core-shell p-n junction nanowires for the fabrication of all-inorganic metal oxide/ sulphide nanowire solar cells. In addition research activites are focused on supercapacitors based on metal oxide and nitride nanowires.
M.Zervos (1),*, A.Othonos (2) and A.Nassiopoulou (3)
(1) Nanostructured Materials and Devices Laboratory, Department of Mechanical and Manufacturing Engineering ; (2) Center of Ultrafast Science, Department of Physics ; University of Cyprus, PO Box 20537, Nicosia, 1678, Cyprus.
(3) Silicon Nanostructures for Nanoelectronics, Photonics and Sensors Research Group, Nano4NPS, NCSR Demokritos, Institute of Microelectronics, A.Paraskevi, 15310 Athens, Greece.
*e-mail: zervos@ucy.ac.cy
Metal oxide semiconductor nanowires (NWs) such as SnO2 [1] In2O3 [2] ,Sn doped In2O3 [3] and Ga2O3 [4,5], are important for the fabrication of nansocale devices such as nanowire solar cells (NWSC’s). One of the main issues concerning the fabrication of high performance NWSC’s is surface passivation which is critical due to their large surface to volume ratio. In particular the surface passivation of metal oxide (MO) NWs is required to suppress the adsorption and desorption of oxygen which has been demonstrated by applying polyimide and polymethylmethacrylate on SnO2 NWs [6,7]. Sulfur passivation has only been applied to InAs and GaAs NWs [8] not MO NWs. On the other hand the conversion of MO into metal-sulphide (MS) NWs is also important for photocatalysis [9].
Here I will give an overview of our work on the growth and properties of MO NWs but more importantly their conversion into MS NWs and show how it is possible to tailor their electronic and optical properties so that they may be included in NWSCs [10]. Then the growth of Sn doped Ga2O3 NWs and their conversion into Ga2S3 NWs will be described in detail. We have grown Sn doped Ga2O3 NWs on 1 nm Au/Si(001) at 800°C and 1 mBar via the vapour-liquid-solid (VLS) mechanism and exposed these to 50 sccms H2S between TS = 300-900°C for 60 min. We observe the conversion of Ga2O3 into -Ga2S3 above TS = 500°C as confirmed by x-ray diffraction (XRD). More importantly the sulphur passivation of the Sn doped Ga2O3 NWs at TS = 500°C results into the emergence of red photoluminescence at 680 nm observed at room temperature which may be used for energy down conversion and improving the efficiency of Si solar cells.
References
[1]D.Tsokkou, A.Othonos and M.Zervos, Appl.Phys.Lett.,100, p.133101 (2012).
[2] D.Tsokou, M.Zervos and A.Othonos, Journal Of Applied Physics 106, p. 084307 (2009).
[3] M.Zervos, C.Mihailescu, J.Giapintzakis, N.Florini, Ph.Komninou, Appl.Phys.Lett.Mats,2, p.0156104(2014).
[4]A.Othonos, M.Zervos and C.Christofides, Journal Of Applied Physics, 108, p.124302 (2010).
[5] A.Othonos, M.Zervos and C.Christofides, ‘Journal of Applied Physics, 108, p124319(2010).
[6] J.Huh, M.K.Joo, D.Jang, J.H.Lee and G.T.Kim, J.Mater.Chem, 22,p.24012(2012).
[7] W.I.Park, J.S.Kim, G.C.Yi, M.H.Bae and H.J.Lee, Appl.Phys.Lett., 85, p.5052(2004).
[8]K.L.Vugt,S.J.Veen, E.P.A.M. Bakkers, A.L.Roest and D.Vanmaekelbergh, J.Am.Chem.Soc.127,p.12357(2005).
[9]Y.C.Zhang, Z.N.Du, K.W.Li, M.Zhang, D.Dionysiou, ACS Appl.Mater.Interfaces,3,p.1528(2011).
[10] E.Karageorgou, M.Zervos and A.Othonos, Applied Physics Letters Materials 2,116107(2014).