The electrical and detection properties of the X/gamma-ray detectors, fabricated using commercial detector-grade p-like CdTe single crystals grown by Acrorad Co., were studied. The detectors were developed as Cr/CdTe/Au Schottky diodes using CdTe wafers with an area of 5 × 5 mm2 and different thicknesses (0.25, 0.5, 0.75, 1.0 and 2.0 mm). Both the Schottky and Ohmic contacts were formed on the opposite sides of semi-insulating CdTe(111) crystals after preliminary chemical and Ar-ion etchings using different parameters. The Cr/CdTe/Au Schottky diodes demonstrated steep rectification that made it possible to apply high reverse bias voltage up to V = 1500-2000 V at moderately low dark currents. Having the rectifying contact area of 10 mm2, the diodes showed dark currents ~ 2-3 nA at V = 1000 V (T = 300 K). The dominant charge carrier transport mechanisms were analyzed using the I-V characteristics and determined as: generation-recombination in the space-charge region (SCR) at V = 1-100 V, the charge transport in the conditions when the SCR width exceeded the thickness of a semiconductor crystal at elevated voltages and, finally currents limited by space charge at even higher bias voltages. For radiation from a 137Cs radioisotope, the Cr/CdTe/Au detectors fabricated on thin (0.5 mm) semiconductor crystals showed the highest energy resolution (FWHM = 0.5%@662 keV). The detection efficiency increased in 4 times with increasing the crystal thickness (up to 2 mm), although the energy resolution deteriorated from 0.5 % to 3 % that, however, was still acceptable for spectroscopic operation of the detectors.
The 248 nm excimer laser etching characteristic of alumina ceramic and sapphire had been studied using different laser fluence and different number of pulses. And the interaction mechanism of 248 nm excimer laser with alumina ceramic and sapphire had been analyzed. The results showed that when the laser fluence was less than 8 J/cm2, the etching depth of alumina ceramic and sapphire were increased with the increase of laser fluence and number of pulses. At the high number pulses and high-energy, the surface of the sapphire had no obvious melting phenomenon, and the alumina ceramic appeared obvious melting phenomenon. The interaction mechanism of excimer laser with alumina ceramics and sapphire was mainly two-photon absorption. But because of the existence of impurities and defects, the coupling between the laser radiation and ceramic and sapphire was strong, and the thermal evaporation mechanism was also obvious.
The damages of TEA-CO2 laser to HgCdTe imaging sensor are researched experimentally and theoretically. The shadows, cracks and dark line are observed. There is a gap between photosensitive layer and CdZnTe which decreases light transmittance, so that the shadows occur. It shows that the crack damages begin from photosensitive layer. The sensor is irradiated by pulse laser, the absorptivity of photosensitive layer is strong, sharp temperatures fluctuations inside the sensor, leading to stress. With the stress increased, the cracks are observed on the surface of the detector. Cracked the surface of the substrate, and effective transmission reduced, which caused gray pixel response decline. The dark line in image occurs several times because Hg atoms separate out from the detector and gather together at the Si-COMS which makes a short circuit between silicon substrate and signal choice line. The volatility of Hg makes the short circuit is unstable, resulting in the dark line repeated in the output image, but the short circuit occurs by chance.
Excimer laser in condition of high voltage, large current and fast discharge will produce strong electromagnetic pulse radiation and electromagnetic interference on the around electrical equipment. The research on characteristics and distribution of excimer laser electromagnetic radiation could provide important basis for electromagnetic shielding and suppressing electromagnetic interference, and further improving the electromagnetic compatibility of system. Firstly, electromagnetic radiation source is analyzed according to the working principle of excimer laser. The key test points of the electromagnetic radiation, hydrogen thyratron, main discharge circuit and laser outlet, are determined by the mechanical structure and the theory of electromagnetic radiation. Secondly, characteristics of electromagnetic field were tested using a near field probe on the key positions of the vertical direction at 20, 50, and 80 cm, respectively. The main radiation frequencies and the radiation field characteristics in the near field are obtained. The experimental results show that the main radiation frequencies distribute in 47, 65, and 130 MHz for electric field and the main radiation frequencies distribute in 34, 100, and 165 MHz for magnetic field. The intensity of electromagnetic field decreases rapidly with the increase of test distance. The higher the frequency increases, the faster the amplitude attenuate. Finally, several electromagnetic interference suppression measurement methods are proposed from the perspective of electromagnetic compatibility according to the test results.
The theoretical model of K9 glass irradiated by a 248-nm KrF excimer laser was established, and a numerical simulation was performed to calculate temperature and thermal stress fields in the K9 glass sample using the finite element method. The laser-induced damage thresholds were defined and calculated, and the effect of repetition frequency and the number of pulses on the damage threshold were also studied. Furthermore, the experiment research was carried out to confirm the numerical simulation. The damage threshold and damage morphology were analyzed by means of a metallurgical microscope and scanning electron microscopy. The simulation and experimental results indicated that the damage mechanism of K9 glass irradiated by a KrF excimer laser was melting damage and stress damage, and the stress damage first appeared inside the K9 glass sample. The tensile stress damage threshold, the compressive stress damage threshold, and the melting damage threshold were 0.64, 0.76, and 1.05 J/cm2, respectively. The damage threshold decreased with increasing repetition frequency and number of laser pulses. The experimental results indicated that the damage threshold of K9 glass was 2.8 J/cm2.
The optical component of photoelectric system was easy to be damaged by irradiation of high power pulse laser, so the effect of high power pulse laser irradiation on K9 glass was researched. A thermodynamic model of K9 glass irradiated by ultraviolet pulse laser was established using the finite element software ANSYS. The article analyzed some key problems in simulation process of ultraviolet pulse laser damage of K9 glass based on ANSYS from the finite element models foundation, meshing, loading of pulse laser, setting initial conditions and boundary conditions and setting the thermal physical parameters of material. The finite element method (FEM) model was established and a numerical analysis was performed to calculate temperature field in K9 glass irradiated by ultraviolet pulse laser. The simulation results showed that the temperature of irradiation area exceeded the melting point of K9 glass, while the incident laser energy was low. The thermal damage dominated in the damage mechanism of K9 glass, the melting phenomenon should be much more distinct.
Excimer laser with nanosecond pulse duration can induce low thermal budget processing and heating confinement near the surface region, which make excimer laser annealing process suitable for low-temperature growth of oxide films. This work presented 248 nm KrF excimer laser irradiation processes of ZnO films prepared by a DC magnetron sputtering method. The influence of the laser energy densities on the structural, morphology, optical and electrical characteristics of ZnO films were investigated. The results presented that the crystallinity of ZnO films could be raised obviously by the excimer laser annealing process. The film under laser irradiation with 137 mJ/cm2 outputs showed the lowest sheet resistance of 10 kΩ/□ and high visible transmittance (~77.4%). This study indicated that excimer laser annealing is a useful method for the performance improvement of oxide films.
The damage of K9 glass under 248nm ultraviolet pulsed laser irradiation was studied. The laser pulse energy was kept within the range of 60mJ to 160mJ, and the repetition rate was adjusted within the range of 1Hz to 40Hz. The damage morphologies of single-pulse and multi-pulse laser irradiation were characterized by optical microscope, and the damage mechanism was discussed. The experimental results indicated that the damage of K9 glass irradiated by 248nm ultraviolet laser mainly followed the thermal-mechanical coupling mechanism and the damage threshold of K9 glass was 2.8J/cm2. The intensity of damage area increased gradually with the increase of the laser pulse number. It was shown that accumulation effect of laser induced damage to K9 glass was obvious.
Transparent conducting CuCr1-xMgxO2 thin films were prepared by pulsed laser deposition (PLD) from polycrystalline
CuCr1-xMgxO2 targets. The derived CuCr1-xMgxO2 films were highly c-axis oriented deposited at higher substrate
temperature. The micro structural, electrical as well as optical properties were studied. It was found that the films were
relatively smooth, and behaved as semiconductors. The transmittances of the films in the visible region are about 80%
with direct band gaps about 3.15eV. The results suggested that CuCr1-xMgxO2 films could be successfully prepared by
PLD, which can broaden the applications of the transparent conducting oxides films.
Strong room temperature ultraviolet emission is observed in highly oriented ZnO microcrystallite films prepared on (001) sapphire substrates by pulsed laser deposition method (PLD). The influences of substrate temperature, distance between the target and the substrate, oxygen pressure, and laser energy density on structural and optical properties were systemically studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and room temperature photoluminescence (PL) measurements. The XRD as well as the SEM results showed that all the four experiment parameters had obvious effects on the structure and micrograph of the derived ZnO films. From the room temperature photoluminescence spectra, all the derived samples have a strong ultraviolet (UV) emission about 376nm, and the visible emission is depressed greatly. Additionally, the results showed that the processing parameters could obviously affect the PL properties and the reasons were also discussed. From our results, the UV PL intensity is strongly depending both on the crystallinity and the stoichiometry of the ZnO films.
In spite of the advantage of droplet reduction in the pulsed laser deposition (PLD) process, eclipse PLD method has some drawbacks that activated growth species are also shielded by the shadow mask, and deposition rate decreases in low ambient pressure condition. In this study, we proposed new composite shadow mask method named 'eclipse angel PLD method' to overcome this problem. We directly observed the emitting plume propagating through the ring-mask structure and reaching the substrate by the ultra fast camera, and confirmed growth rate enhancement of YBa2Cu3Ox thin films in low ambient oxygen pressure region. Also, did we the effects of Ar addition when are of favor to improve the film qualities of Bi-layered crystals.
RuO2 thin films have been grown by the pulsed laser deposition (PLD) method. It was shown that the RuO2 thin film were (110) oriented and in-plane ordered (epitaxially grown). The electrical and optical properties of the RuO2 thin film have been measured. When grown at 700 degrees Celsius, the films exhibited resistivities as low as 39 (mu) (Omega) (DOT) cm at room temperature. The real and imaginary parts of the dielectric constant and complex refractive index for RuO2 thin films were estimated in the photon energy range from 1.5 to 4.5 eV by spectroscopic ellipsometry measurements. A transition from the valence band to the conduction band was observed for RuO2 thin films near 2.7 eV and the dependence of the refractive index on the deposition temperature was also observed.
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