Dependence of band structure and carrier concentration of metallic (13, 13) and semiconducting (13, 0) single wall carbon nanotube on temperature

The electronic band structure, density of states (DOS) and carrier concentration of a (13,13) metallic and a (13,0) semiconducting Single Wall Carbon Nanotube (SWCNT) have been estimated and simulated by using the Fermi-Dirac distribution function. The energy dispersion E(k) relation for metallic SWCNT near the minimum energy is linear and the Fermi level was independent of temperature (T). On the other hand for semiconducting SWCNT the E(k) relation is parabolic. The normalized Fermi-Energy (EF – EC) in the nondegenerate regime is a weak (logarithmic) function of carrier concentration and varies linearly with T. In the degenerate condition, the Fermi level was independent of T and was a strong function of carrier concentration

Effects of annealing conditions on the surface morphology and crystallinity of sputtered ZnO nano films

The effects of annealing parameters on crystallinity and surface morphology of RF sputtered zinc oxide nano films were investigated. The structure and morphology of the nano films were dependent on temperature, gas flow rate and time of annealing. The results from atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) showed smooth and uniform growth of c-axis orientation films with an average grain sizes from 10 to 30 nm. Increments of the annealing temperature from 400 to 800°C led to bigger grain size, better crystallinity and also increase of the surface roughness. Moreover, the results showed that the crystallinity was independent of the annealing time up to 40 min after starting the annealing process. Increase in the percentage of oxygen in the O/Ar (mixture of annealing gases) from 50% to 100% results in no changes in AFM results, but XRD revealed that the (100) peak intensity was decreased, the position of (002) peak was slightly shifted towards higher angle and FWHM of (002) peak was improved

Condenser microphone with small size and high sensitivity Using a circular diaphragm with fixed center

In this paper, a new single-chip MEMS capacitor microphone on a silicon wafer by minimizing the size and the reduction of mechanical strength using a circular diaphragm with a fixed center is proposed. In the proposed microphone, the diaphragm includes a number of holes to pass the air through the gap between the back plate and diaphragm, and thus reduces the damping of the sound from the microphone. Novelty of this method, creating a circular microphone with fixed center, which the diameter of diaphragm is less than the conventional condenser microphone. At first, the mechanical analysis was conducted on microphone diaphragm in order to achieve the pull-in voltage. The pull-in voltage of the proposed circular microphone is 14 volts. According to the obtained pull-in voltage, the bias voltage were applied to the microphone, and various parameters such as capacitance and sensitivity were measured. Based on the simulation results of COMSOL, the proposed microphone with diaphragm diameter of 400 μm and a thickness of 1.5 μm, the sensitivity of -23 dB is shown. In comparison with previous works, the proposed microphone with lower supply voltage is provided the better frequency performance, and higher sensitivity, in order to sense the sound

Black phosphorus mid infrared photodetector with circular Au/Pd antennas

Black phosphorus has been considered as oneof the most capable two-dimensional materials for use inoptoelectronic nanodevices due to its intrinsic layerednature structure, high mobility of carrier, and tunablebandgap. But its low light absorption prevents its use inhigh-efficiency photodetectors. In this study, the circularAu/Pd antenna-assisted black phosphorus mid-infraredphotodetector which significantly improves the detectionperformance in comparison with BP photodetectorswithout antenna has been proposed. By integrating acircular Au/Pd antenna on the BP surface, the light-BPinteraction was significantly increased. The simulationresults demonstrate that metallic antenna structuresimprove both light absorption and photocarrier collectionin BP phosphorus detectors. The numerical result showsthat the photocurrent of the mid-infrared antenna-assistedBP detector was 5 times larger than that of BPphotodetector without antennas

Synthesis and characterization of well-aligned catalyst-free phosphorus-doped ZnO nanowires

10.1016/j.jallcom.2011.09.018Journal of Alloys and Compounds512168-72JALC

Analysis and simulation of carriers statistic for semiconducting single wall carbon nanotube

In scaling down to 10 nm, the electron transportation is predominantly ballistic. Moreover, in most of the doped nanoscale devices, the carrier density is in the degenerate regime. In these cases the failure of Boltzmann statistic has led the research to new explanations. In this paper the authors formulate and simulate the carrier concentration in a semiconducting single wall carbon nanotube using the Fermi-Dirac distribution function. It was shown that the band structure of semiconducting single wall carbon nanotube nearby the minimum energy is parabolic and density of state is proportional to the Fermi-Dirac distribution. In the non-degenerate regime, Fermi energy is a weak logarithmic function of carrier concentration and varies linearly with temperature, but for strongly degenerate statistics, the Fermi energy is a strong function of carrier concentration and is independent of temperature