• MUKUL GUPTA

Articles written in Bulletin of Materials Science

• Influence of annealing temperature on ZnO thin films grown by dual ion beam sputtering

We have investigated the influence of in situ annealing on the optical, electrical, structural and morphological properties of ZnO thin films prepared on 𝑝-type Si(100) substrates by dual ion beam sputtering deposition (DIBSD) system. X-ray diffraction (XRD) measurements showed that all ZnO films have (002) preferred orientation. Full-width at half-maximum (FWHM) of XRD from the (002) crystal plane was observed to reach to a minimum value of 0.139° from ZnO film, annealed at 600 °C. Photoluminescence (PL) measurements demonstrated sharp near-band-edge emission (NBE) at ∼ 380 nm along with broad deep level emissions (DLEs) at room temperature. Moreover, when the annealing temperature was increased from 400 to 600 °C, the ratio of NBE peak intensity to DLE peak intensity initially increased, however, it reduced at further increase in annealing temperature. In electrical characterization as well, when annealing temperature was increased from 400 to 600 °C, room temperature electron mobility enhanced from 6.534 to 13.326 cm2/V s, and then reduced with subsequent increase in temperature. Therefore, 600 °C annealing temperature produced good-quality ZnO film, suitable for optoelectronic devices fabrication. X-ray photoelectron spectroscopy (XPS) study revealed the presence of oxygen interstitials and vacancies point defects in ZnO film annealed at 400 °C.

• Negative capacitance effect of Cu–TiC thin film deposited by DC magnetron plasma

The quest for low power consumption devices with new functionalities has made the negative capacitance (NC) effect, the most captivating and studied phenomenon. The NC effect is observed in Cu–TiC thin film at a low frequencyrange between 112.9 Hz and 2 kHz. The Cu–TiC thin film was deposited on Si (100) substrate by DC magnetron co-sputtering process and then annealed in a vacuum at different temperatures (100–600$^{\circ}$C). The magnitude ofNC increased from $-$0.016 to $-$27.5 lF after annealing. The NC behaviour is also observed in the forward biased region of the capacitance–voltage ($C–V$) characteristics. The current–voltage ($I–V$) characteristics reveal the decreasing static and dynamic resistance for higher annealed films. An improved electrical conductivity ($27.70 \times 10^3$ to $384.62 \times 10^3$ S m$^{-1}$)is evidenced with decreasing ideality factor (2.01–0.55) in the post-annealed films. The films were found to be polycrystalline from X-ray diffraction patterns with Cu and TiC phases. Raman studies have also confirmed the presence of Cuand TiC vibrational modes in all films. The intensity of C peaks detected at 1359 cm$^{-1}$ (D peak) and at 1590 cm$^{-1}$ (G peak) in the as-deposited film decreased after annealing. The annealing effect reduced the amount of unreacted carbon and contributed to form stoichiometric TiC from non-stoichiometric TiC.

• # Bulletin of Materials Science

Volume 43, 2020
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020