Research on Trimming Frequency-Increasing Technology for Quartz Crystal Resonator Using Laser Etching.

A quartz crystal resonator (QCR) is an indispensable electronic component in the field of the modern electronics industry. By designing and depositing electrodes of different shapes and thicknesses on a quartz wafer with a certain fundamental frequency, the desired target frequency can be obtained. Affected by factors such as the deposition equipment, mask, wafer size and placement position, it is difficult to accurately obtain the target frequency at a given time, especially for mass-produced QCRs. In this work, a laser with a wavelength of 532 nm was used to thin the electrodes of a QCR with a fundamental frequency of 10 MHz. The electrode surface was etched through a preset processing pattern to form a processing method of local thinning of the electrode surface. At the same time, the effect of laser etching on silicon dioxide and resonator performance was analyzed. Satisfactory trimming frequency-increasing results were achieved, such as a frequency modulation accuracy of 1 ppm, frequency distribution with good consistency and equivalent parameters with small changes, by the laser partial etching of the resonator electrode. However, when the surface electrode was etched into using through-holes, the attenuation amplitude of the equivalent parameter became larger, especially in terms of the quality factor (Q), which decreased from 63 K to 1 K, and some resonators which had a serious frequency drift of >40%. In this case, a certain number of QCRs were no longer excited to vibrate, which was due to the disappearance of the piezoelectric effect caused by the local thermal phase change in the quartz wafer.

[The impact of ZnS/CdS composite window layer on the quantun efficiency of CdTe solar cell in short wavelength].

ZnS/CdS composite window layer was prepared by magnetron sputtering method and then applied to CdTe solar cell. The morphology and structure of films were measured. The data of I-V in light and the quantum efficiency of CdTe solar cells with different window layers were also measured. The effect of ZnS films prepared in different conditions on the performance of CdTe solar cells was researched. The effects of both CdS thickness and ZnS/CdS composite layer on the transmission in short wavelength were studied. Particularly, the quantum efficiency of CdTe solar cells with ZnS/CdS window layer was measured. The results show as follows. With the thickness of CdS window layer reducing from 100 to 50 nm, the transmission increase 18.3% averagely in short wavelength and the quantum efficiency of CdTe solar cells increase 27.6% averagely. The grain size of ZnS prepared in 250 degrees C is smaller than prepared at room temperature. The performance of CdTe solar cells with ZnS/CdS window layer is much better if ZnS deposited at 250 degrees C. This indicates grain size has some effect on the electron transportation. When the CdS holds the same thickness, the transmission of ZnS/CdS window layer was improved about 2% in short wavelength compared with CdS window layer. The quantum efficiency of CdTe solar cells with ZnS/CdS window layer was also improved about 2% in short wavelength compared with that based on CdS window layer. These indicate ZnS/CdS composite window layer can increase the photon transmission in short wavelength so that more photons can be absorbed by the absorbent layer of CdTe solar cells.

Spectral analysis of the effects of 1.7 MeV electron irradiation on the current transfer characteristic of cadmium telluride solar cells.

The effects of device performance of 1.7 MeV electron irradiation on cadmium telluride polycrystalline thin film solar cells with the structure of anti-radiation glass/ITO/ZnO/CdS/CdTe/ZnTe/ZnTe : Cu/Ni have been studied. Light and dark I-V characteristics, dark C-V characteristics, quantum efficiency (QE), admittance spectrum (AS) and other testing methods were used to analyze cells performance such as the open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF) and conversion efficiency (eta). It was explored to find out the effects of irradiation on the current transfer characteristic of solar cells combined with the dark current density (Jo), diode ideal factor (A), quantum efficiency, carrier concentration and the depletion layer width. The decline in short-circuit current was very large and the efficiency of solar cells decreased obviously after irradiation. Reverse saturation current density increased, which indicates that p-n junction characteristics of solar cells were damaged, and diode ideal factor was almost the same, so current transport mechanism of solar cells has not changed. Quantum efficiency curves proved that the damage of solar cells' p-n junction influenced the collection of photo-generated carriers. Irradiation made carrier concentration reduce to 40.6%. The analyses have shown that. A new defect was induced by electron irradiation, whose position is close to 0.58 eV above the valence band in the forbidden band, and capture cross section is 1.78 x 10(-16) cm2. These results indicate that irradiation influences the generation of photo-generated carriers, increases the risk of the carrier recombination and the reverse dark current, and eventually makes the short-circuit current of solar cells decay.

[Preparation and properties of P-type Cd1-xZn(x)Te thin films].

Cd1-xZnxTe:Cu Thin films were prepared by co-evaporation method. X-ray Fluorescence Spectrometry (XRF), scanning electron microscope(SEM), UV-Vis transmission spectra, thermal probe, four-probe method, step profiler and X-ray diffractometer (XRD) were used to investigate the composition, structure, morphology, optical and electrical properties of Cd1-x ZnxTe:Cu thin films with different doping concentration. The results show that the resistivity of 10% copper doped Cd1-x ZnxTe films increased several magnitude and the conductive type changed from p-type to n-type after annealing. The 20% cu-doped Cdl, Zn,Te films had not obvious change in conductive type and electrical resistivity after annealing and they exhibit good surface morphology. The transmissivity of 30% cu-doped Cd1-x, ZnxTe films decreased seriously below 10% after annealing, which indicate that they are not suitable to be the top cell materials in tandem structure. The 20% and 30% cu-doped Cd1-x Zn, Te films were both p-type conductivity.

[Study of the physical properties of SnS thin films deposited by ultrasonic spray pyrolysis method].

In the present paper, SnS thin films were deposited by ultrasonic spray pyrolysis method. The influence of the three different precursor concentrations on the properties of SnS thin films was compared. XRD shows that when precursor solution is thiourea (0.5 mol x L(-1)) + tin tetrachloride (0.5 mol x L(-1)) + deionized water, there are SnS and SnO2 mixed phases; when precursor solution is thiourea (0.6 mol x L(-1)) + tin tetrachloride (0.5 mol x L(-1)) + deionized water, SnS phase is the dominant diffraction peak, although a certain amount of SnO2 phase is contained; when precursor solution is thiourea (0.7 mol x L(-1)) + tin tetrachloride (0.5 mol x L(-1)) + deionized water, thin film after being annealed is single SnS thin film with orthorhombic structure. SEM shows that films are uniform and dense. Furthermore, the particles of films are bigger when thiourea concentration is higher. Transmittance spectrum shows that the influence of precursor concentration on transmittance of thin films is less. Dark I-V and C-V tests of the devices show that junction characteristics of the devices were similar when prepared by three different concentrations of precursor solution, and as the thiourea concentration is higher, the carrier concentration is relatively larger.

[Spectral analysis of effects of annealing on the characteristics of intrinsic SnO2 polycrystalline thin films].

In order to improve the conversion efficiency of the CdTe solar cells, it is necessary to decrease the thickness of CdS layer. However, the decrease in CdS thickness may lead to adverse effects on the solar cells. Therefore, a high-resistance transparent layer (intrinsic SnO2) has been used as a buffer layer between the transparent conducting oxide (TCO) and CdS layer. In the present paper, SnO2 polycrystalline thin films were prepared by magnetic reactive sputtering. The properties of the films before and after annealing were studied by XRD and XPS. The results revealed that the films annealed at 550 degrees C for 30 minutesare polycrystalline SnO2 with a single phase of tetragonal structure and have orientation of (110) direction. XPS investigation shows that after annealing the oxygen content of the film increases, O1s peak shifts to lower energies, and SnO is oxidized into SnO2, After annealing the intrinsic SnO2 films of high-resistance as a buffer layer are very suitable for the CdTe solar cells.