Structural and optical investigations of cobalt oxide nanoparticles

Abstract

Two stable phases of cobalt oxide nanoparticles of controlled sizes have been synthesized using environ- mentally friendly inorganic precursor. Structural charac- terization using X-ray diffraction (XRD) shows a single- phase spinal Co3 O4 structure up to annealing temperature of 800 °C and a mixed phase of Co3 O4 and CoO particles for T > 900 °C. Single-phase CoO nanoparticles are also obtained by annealing the particles at a temperature >900 °C and cooling in inert atmosphere. Average macro- and micro- strain were estimated using XRD data. Macrostrain was found to be the minimum for particles annealed at 600 °C, whereas microstrain was found to decrease with increasing annealing temperature up to 900 °C. A correlation between the density of localized states (DOS) in the band gap and strain is expected because the origin of both strain and DOS are defects and bond length distortions. Sub-gap absorption measurement and model calculations have been used for the determination of DOS. For cobalt oxide nanoparticle sam- ples we find a correlation between estimated strain and den- sity of states in the band gap.

Investigated electronic and structural properties of non-metallic elements doped BP

“…The energy convergence criterion is set to 10 -4 eV. In the process of structural optimization and selfconsistent calculation, we selected 5 ×5×1 and 10×10×1 for the k-point grid of Brillouin zone [5][6][7][8][9]. Figure 1 shows all the structural models designed in this paper: Figure 1 (a) presents the configuration of l BP (3 ×3), and the site of one P vacancy defect is marked, as well as bond lengths d1 and d2.…”

Optical properties of HfO2 nanostructures for optoelectronic device

“…HFO2 has a high reflective index ~2 [6][7][8] and a high reaction free energy with silicon about 79.6 kcal/mol at 1000 K compared with TiO2 and Ti2O5 [9][10][11][12][13]. In addition, HFO2 is a high refactory material with excellent chemical and physical properties which are led to use the HFO2 films in many applications [14][15][16][17][18]. Karaduman et al reported that the sensitivity of HFO2 films increased after 30 min of Uv radiation, which is referred to the ability of these films to be a good gas sensor after radiation by ultra-violate [19][20][21][22][23].…”

Analysis and characterization of GaN nanostructure by electrochemical etching

“…Several have attempted to investigate compound semiconductors nanostructure such as GaAs, GaP and GaN [1][2][3][4][5] while the most suitable etching method is still not concrete because of the excellent chemical stability and high hardness of these compounds. Plasma etching [6] and reactive ion etching (RIE) [7,8] have mainly been applied so far to etching of III-V nitride crystals. With these processes, however, damage by ion or plasma bombardment is a serious problem.…”