• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.336-336
• /
• 2012

수명 측정법과 동시 계수 도플러 넓어짐 양전자 소멸 분광법으로 p형과 n형 실리콘 시료에 0, 3.98 MeV 에너지를 가진 $0.0{\sim}20.0{\times}10^{13}$ protons/$cm^2$ 양성자 빔 조사에 의한 결함을 측정하여 실리콘 결함 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 감마선 스펙트럼의 전자 밀도 에너지를 수리적 해석 방법인 S-변수와 열린 부피 결함에 대한 측정법으로서 양전자 수명 ${\tau}1$과 ${\tau}2$, 이에 따른 밀도 I1과 I2를 사용하여, 시료의 구조 변화를 측정하였다. 본 연구에서 측정된 S-변수와 양전자 수명은 시료에 조사된 양성자의 빔 에너지에 따라 변화하기보다 양성자 조사량의 변화에 따라 결함이 증가하였으며, 양전자 수명 측정과 같은 경향을 보여준다. SRIM의 결과로써, 양성자 조사 에너지에 따른 Bragg 피크 때문에 양성자는 시료의 특정 깊이에 주로 결함을 형성하여 시료 전체에는 결함으로 잘 나타나지 않기 때문이다. 빔의 조사량에 따른 결함의 영향이 더 큰 것으로 나타났다.

• Journal of the Korean Vacuum Society
• /
• v.21 no.5
• /
• pp.225-232
• /
• 2012

It is described that the proton beam induceds micro-size defects and electronic deep levels in n or p type single crystal silicon. Positron lifetime and Coincidence Doppler Broadening Positron Annihilation Spectroscopy were applied to study of characteristics of p type and n type silicon samples. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The samples were exposed by 3.98 MeV proton beams ranging between 0 to ${\sim}10^{14}$ particles. The S-parameter values strongly depend on the irradiated proton beam, that indicated the defects generate more. Positron lifetime shows that positrons trapped in vacancies and lifetime ${\tau}_2$ increased according to proton irradiation.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.45.1-45.1
• /
• 2009

본 연구에서는 BaSrFBr:Eu 형광물질의 결함 농도 분석을 시도하였다. 또한 동시 계수 방법과 Fast -Slow - Coincidence 시스템으로 구성한 양전자 수명 측정법을 통하여 에너지의 변화에 따른 양성자 조사에 의한 시료 결함에 따른 동시 계수 도플러법과 양전자 수명의 변화를 측정 하였으며, SRIM 시뮬레이션을 통한 에너지에 따른 양성자 투과 깊이의 변화를 연구하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.259-259
• /
• 2010

본 연구는 양전자 소멸 측정 분광법을 통하여 BaSrFBr:Eu 형광물질의 결함 농도 분석을 시도하였다. LABO를 이용한 동시계수 도플러 방법과 Fast - Slow - Coincidence 시스템으로 구성한 양전자 수명 분광법을 통하여 에너지의 변화에 따른 양성자 조사에 의한 시료 결함에 따른 동시 계수 도플러법과 양전자 수명의 변화를 측정 하였으며, SRIM 시뮬레이션을 통한 에너지에 따른 양성자 투과 깊이의 변화를 연구하였다.

• Journal of the Korean Vacuum Society
• /
• v.22 no.5
• /
• pp.250-256
• /
• 2013

It is described that the proton beam induces micro-size defects and electronic deep levels in luminescence Thin Film. Coincidence Doppler Broadening Positron Annihilation Spectroscopy (CDBPAS) and Positron lifetime Spectroscopy were applied to study of characteristics of a poly crystal samples. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S-parameter value. The samples were exposed by 3.0 MeV proton beams with the intensities ranging between 0 to ${\sim}10^{14}$ particles. The S-parameter values decreased as increased the proton beam, that indicates the protons trapped in vacancies. Lifetime ${\tau}_1$ shows that positrons are trapped in mono vacancies. Lifetime ${\tau}_2$ is not changed according to proton irradiation that indicate the cluster vacancies of the grain structure.

• Journal of the Korean Vacuum Society
• /
• v.18 no.6
• /
• pp.447-452
• /
• 2009

Enhance signal-to-noise ratio, Coincidence Doppler Broadening positron method has been applied to study of characteristics of BaSrFBr:Eu film sample. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The films were exposed by 0, 3, 5, and 7.5 MeV proton beams ranging from 0 to $10^{13}$ ptls. The S-parameter values were increased as increasing the exposed time and the energies, that indicated the defects generate more.

• Journal of Astronomy and Space Sciences
• /
• v.25 no.4
• /
• pp.435-444
• /
• 2008

High energy charged particles are trapped by geomagnetic field in the region named Van Allen Belt. These particles can move to low altitude along magnetic field and threaten even low altitude spacecraft. Space Radiation can cause equipment failures and on occasions can even destroy operations of satellites in orbit. Sun sensors aboard Science and Technology Satellite (STSAT-l) was designed to detect sun light with silicon solar cells which performance was degraded during satellite operation. In this study, we try to identify which particle contribute to the solar cell degradation with ground based radiation facilities. We measured the short circuit current after bombarding electrons and protons on the solar cells same as STSAT-1 sun sensors. Also we estimated particle flux on the STSAT-l orbit with analyzing NOAA POES particle data. Our result clearly shows STSAT-l solar cell degradation was caused by energetic protons which energy is about 700keV to 1.5MeV. Our result can be applied to estimate solar cell conditions of other satellites.

• Korean Journal of Materials Research
• /
• v.20 no.6
• /
• pp.307-311
• /
• 2010

Positron annihilation lifetime spectroscopy is applied to BaSrFBr : Eu film which is used for the phosphore layer, and afterwards the reliability and self-consistency of source corrections in the positron lifetime spectroscopy is investigated using a $^{22}Na$ positron emitter covered by thin foils. The positron lifetime showed no significant change through the various proton irradiation energies. It is unusual that the measurements of the defects indicate that most of the defects were likely to have been generated by X-ray radiation. This may have resulted from the Bragg peaks of the proton characteristics. The Bragg peak does not affect the defect signals enough to distinguish the lifetimes and intensities in a material that is includes multi-grains. The lifetime ($\tau_1$) associated with positron annihilations in the Ba, Br, and Eu of the sample was about 250 ps, and due to the annihilations at F-centers or defects from the irradiated protons in sample, the lifetime ($\tau_2$) was about 500 ps.

• Journal of the Korean Chemical Society
• /
• v.37 no.3
• /
• pp.271-278
• /
• 1993

The hyperfine splitting constants of phenanthrenequinone anion radical have been determined for the solution of triethylamine with 2-propanol, 2-pentanol or benzene by cwESR and time-resolved ESR methods. The radical anion was produced by photolysis using a pulsed excimer laser. The resulting hyperfine splitting constant A$_{H1}$ and A$_{H2}$ are 1.662, 0.378 in 2-propanol, 1.602, 0.361 in 2-pentanol and 1.518 in benzene respectively. The hyperfine coupling constants decrease with the decreasing of polarity of the mixed solvent. The tendency of the variation depends on the polarity of the solvents, thus, making it in impossible to observe the magnetic equivalent proton in a mixed solvent of nonpolar benzene. Particularly, time-resolved ESR spectrum of triethylamine radical (TEA${\cdot}$) has been observed in 0.15∼0.30 ${\mu}s$ from the solvent of 3 : 1 with 2-pentanol and triethylamine. Thus from the results of solvent effect, we can suggest that the identification of the unstable short-lived spin polarized phenanthrenequinone anion radical(*PQ${\cdot}^-$) proceed through photochemistry.