Change In Band Energy Research Articles

Band tailoring by annealing and current conduction of Co-doped ZnO transparent resistive switching memory

The switching characteristics of ITO/Zn1-xCoxO/ITO transparent resistive random access memories were studied. 5 mol% cobalt doped ZnO resistive layer improves bipolar switching properties. In addition, the redshift in band energy caused by doping of cobalt (Co) was studied. The doped memory device also showed a change in band energy by 0.1 eV when subjected to annealing of 400 °C. Annealing below 400 °C temperature did not show any characteristic changes. The film morphology analysis suggested the increase in roughness with annealing temperature, which can be seen from FESEM and AFM images. In this study annealing and Co doping effect on ZnO based non-volatile memory device is presented. Moreover, transparent memory devices with 90% transmittance at 550 nm wavelength have been reported. At low field and high field region Schottky emission and ionic conduction are dominated respectively.

Effect of film thickness on topographic, microstructural, optical and dielectric behaviour of PPMBA thin films

Plasma polymerized 2-methyl butylacrylate (PPMBA) thin films of varied thicknesses (d) were deposited on to glass substrates via plasma polymerization technique. FESEM images exhibited that the film of lower thickness was comparatively smoother and uniform than that of the film of higher thickness. Topographic analysis revealed that with the decrease of d from 300 to 120 nm, the mean roughness and root-mean-square roughness decreased from 0.60 to 0.48 and 1.50 to 0.62 nm, respectively. The XRD pattern showed amorphous nature of the PPMBA films. The FTIR band intensity of the spectra of monomer and PPMBA was altered due to change of band energy. The optical T (%) increased rapidly in the lower wavelengths and became nearly constant at higher wavelengths. Refractive index and optical conductivity were reduced from 1.4842 to 1.1252 and 4.2663 × 1014 to 0.1892 × 1014, respectively with the increase in d. The ac conductivity was increased rapidly with frequency (f) but decreased with the increase of d. The dielectric constant (ɛ′) showed a strong dependence on f and d. The maximum ɛ′ was found 4.50 for 300 nm film at 103 Hz. The tanδ peaks shifted a little towards higher f with increasing d, indicating reduction of relaxation time.

The Einstein temperature of itinerant ferromagnets

The Einstein temperature of a tight-binding metal is obtained from the energy required to displace an atom from equilibrium with no movement of neighbouring atoms. In the non-magnetic case the change in repulsive energy between atoms gives a large positive contribution varying parabolically with the number of electrons/atom, whilst the change in band energy acts to reduce theta E, particularly for a half filled band. Magnetism gives a positive contribution to theta E due to the magnetisation dependence of the band distortion energy, and a negative contribution due to the smaller short-range repulsion in the magnetic state.