The action of etching and damage by 20 keV N+ beam on the cells of Deinococcus radiodurans and Escherichia coli was investigated by scanning electron microscope (SEM) and the electron spin resonance (ESR) spectrum of ...The action of etching and damage by 20 keV N+ beam on the cells of Deinococcus radiodurans and Escherichia coli was investigated by scanning electron microscope (SEM) and the electron spin resonance (ESR) spectrum of free radicals. The results showed that N+ implantation exerted the direct action of etching and damage of momentum transferring and the indirect action of the free radicals of energy deposition on their cells, many microholes were found on the surface of cells' wall and /or membrane by SEM, the damaged DNA was determined using DNA unwinding technique, and the signal of free radicals was measured by ESR. The degree of damage to cells by ion beam gradually increased with the increase implantation dose. With the post-treatment of 2 mmol/l caffeine and 0.5 mmol / l Na2-EDTA, the survival rate of D.radiodurans and E.coli further decreased in the order of caffeine > Na2-EDTA > control, and this suggested that low energy ion beam could be implanted into nucleus, doing a damage to DNA and resulting in the mutation of organisms.展开更多
Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular struct...Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.展开更多
The influences of dry-etching damage on the electrical properties of an AlGaN/GaN Schottky barrier diode with ICPrecessed anode was investigated for the first time. It was found that the turn-on voltage is decreased w...The influences of dry-etching damage on the electrical properties of an AlGaN/GaN Schottky barrier diode with ICPrecessed anode was investigated for the first time. It was found that the turn-on voltage is decreased with the increase of dry-etching power. Furthermore, the leakage currents in the reverse bias region above pinch-off voltage rise as radio frequency（RF） power increases, while below pinch-off voltage, leakage currents tend to be independent of RF power.Based on detailed current–voltage–temperature（I–V –T） measurements, the barrier height of thermionic-field emission（TFE） from GaN is lowered as RF power increases, which results in early conduction. The increase of leakage current can be explained by Frenkel–Poole（FP） emission that higher dry-etching damage in the sidewall leads to the higher tunneling current, while below pinch-off voltage, the leakage is only related to the AlGaN surface, which is independent of RF power.展开更多
GaN films with reactive ion etching （RIE） induced damage were analyzed using photoluminescence （PL）. We observed band-edge as well as donor-acceptor peaks with associated phonon replicas, all in agreement with pre...GaN films with reactive ion etching （RIE） induced damage were analyzed using photoluminescence （PL）. We observed band-edge as well as donor-acceptor peaks with associated phonon replicas, all in agreement with previous studies. While both the control and damaged samples have their band-edge peak location change with temperature following the Varshni formula, its intensity however decreases with damage while the D-A peak increases considerably. Nitrogen post-etch plasma was shown to improve the band edge peak and decrease the D-A peak. This suggests that the N2 plasma has helped reduce the number of trapped carriers that were participating in the D-A transition and made the D°X transition more active, which reaffirms the N2 post-etch plasma treatment as a good technique to heal the GaN surface, most likely by filling the nitrogen vacancies previously created by etch damage.展开更多
基金This work is supported by the National Science Foundation of china (19605005)
文摘The action of etching and damage by 20 keV N+ beam on the cells of Deinococcus radiodurans and Escherichia coli was investigated by scanning electron microscope (SEM) and the electron spin resonance (ESR) spectrum of free radicals. The results showed that N+ implantation exerted the direct action of etching and damage of momentum transferring and the indirect action of the free radicals of energy deposition on their cells, many microholes were found on the surface of cells' wall and /or membrane by SEM, the damaged DNA was determined using DNA unwinding technique, and the signal of free radicals was measured by ESR. The degree of damage to cells by ion beam gradually increased with the increase implantation dose. With the post-treatment of 2 mmol/l caffeine and 0.5 mmol / l Na2-EDTA, the survival rate of D.radiodurans and E.coli further decreased in the order of caffeine > Na2-EDTA > control, and this suggested that low energy ion beam could be implanted into nucleus, doing a damage to DNA and resulting in the mutation of organisms.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2016M592709)the National Natural Science Foundation of China(Grant No.51535003)
文摘Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51177175 and 61274039)the National Basic Research Program of China(Grant Nos.2010CB923200 and 2011CB301903)+4 种基金the Ph.D. Programs Foundation of Ministry of Education of China(Grant No.20110171110021)the International Science and Technology Collaboration Program of China(Grant No.2012DFG52260)the National High Technology Research and Development Program of China(Grant No.2014AA032606)the Science and Technology Plan of Guangdong Province,China(Grant No.2013B010401013)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,China(Grant No.IOSKL2014KF17)
文摘The influences of dry-etching damage on the electrical properties of an AlGaN/GaN Schottky barrier diode with ICPrecessed anode was investigated for the first time. It was found that the turn-on voltage is decreased with the increase of dry-etching power. Furthermore, the leakage currents in the reverse bias region above pinch-off voltage rise as radio frequency（RF） power increases, while below pinch-off voltage, leakage currents tend to be independent of RF power.Based on detailed current–voltage–temperature（I–V –T） measurements, the barrier height of thermionic-field emission（TFE） from GaN is lowered as RF power increases, which results in early conduction. The increase of leakage current can be explained by Frenkel–Poole（FP） emission that higher dry-etching damage in the sidewall leads to the higher tunneling current, while below pinch-off voltage, the leakage is only related to the AlGaN surface, which is independent of RF power.
文摘GaN films with reactive ion etching （RIE） induced damage were analyzed using photoluminescence （PL）. We observed band-edge as well as donor-acceptor peaks with associated phonon replicas, all in agreement with previous studies. While both the control and damaged samples have their band-edge peak location change with temperature following the Varshni formula, its intensity however decreases with damage while the D-A peak increases considerably. Nitrogen post-etch plasma was shown to improve the band edge peak and decrease the D-A peak. This suggests that the N2 plasma has helped reduce the number of trapped carriers that were participating in the D-A transition and made the D°X transition more active, which reaffirms the N2 post-etch plasma treatment as a good technique to heal the GaN surface, most likely by filling the nitrogen vacancies previously created by etch damage.
