Current Research
Systems studied
(a)ZnO
(b)Zn1−xMnxO
(c)Si3N4
Characterization techniques used
(a)X-Ray Diffraction.
(b)UV-Visible Absorption Spectroscopy.
(c)Photoluminescence Measurement.
(d)Scanning Electron Microscopy.
(e)Fourier Transform Infrared Transmission Spectroscopy.
(f)Thermogravimetric Analysis.
(g)Positron Annihilation Lifetime Spectroscopy.
(h)Coincidence Doppler broadening of the electron positron annihilation radiation (CDBEPAR) Measurement.
(i)Low Temperature Resistivity Measurements.
(j)Field Dependent and Temperature Dependant DC Magnetization Measurement.
(k)Ion beam irradiation technique.
Short Note on Present Research Work
My doctoral work has been focused on three different systems, Silicon Nitride (Si3N4 ), Mn doped ZnO type dilute magnetic semiconductor (DMS) and pure Zinc Oxide (ZnO). Si3N4 is very much important not only for their interesting properties but also for practical applications. It is widely used, as an insulating material in the semiconductor industry due to its comparable thermal expansion coefficient is to the commonly used semiconductor substrates. Presently we are studying of modification of structural, optical and defect properties with annealing at different temperature under different conditions.
ZnO has promising device applications due to some of its unique properties like large band gap, large exciton binding energy, high optical gain, very short luminescence lifetime etc. High purity ZnO powder samples have been studied in pallet form. All the pallets are sintered at 500 oC for 4 hours and then cooled slowly. The samples have been irradiated by 1.2 MeV Ar8+ ions with different fluence. Study of structural and optical property modification due to irradiation has been carried out. Presently study of ageing and annealing effect on optical properties of these samples is under progress.
Transition metal (Mn, Co, Ni etc.) doped ZnO has potential application in the field of spintronics devices. Mn doped ZnO samples, Zn1-xMnxO have been prepared by conventional solid-state reaction method by using high purity ZnO powder samples and manganese dioxide (MnO2) powder samples. Characterization of structural, optical, electrical and magnetic properties has been carried out. Correlation of defect states with these physical properties is under study. Also investigation on the effect of energetic ion beam on the structural and electrical properties on Zn(Mn)O systems has been carried out. We have irradiated the 2 at% Mn doped ZnO samples by 50 MeV Li3+ ion beam and very interestingly observe insulator to metal transitions.
Grain size dependent modification of structural and optical properties of high purity polycrystalline ZnO by mechanical milling has been done. Defect characterizations of this mechanically milled ZnO samples has been performed from the analysis of band tail parameter and photoluminescence (PL) data. Study of magnetic property modification of mechanically milled nano sized ZnO is under progress.
Presently we are studying the effect of high temperature annealing of ZnO in Ar environment on structural, morphological, optical and electrical properties and on the defect states through XRD, UV-Visible spectroscopy, low temperature and room temperature PL measurement and positron annihilation spectroscopy. We are also trying to explore the facts of generation and recovery of defect states into ZnO due mechanical milling and subsequent annealing using low temperature PL measurement and Positron Annihilation Spectroscopy.