• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.391-394
• /
• 2002

There has recently been much interest and research in developing digital x-ray systems based on using amorphous selenium(a-Se) photoconductors as the image receptor. The amorphous selenium layer that is currently being studied for use as an x-ray photoconductor is not pure a-Se but rather amorphous selenium alloyed with arsenic. We fabricated samples using the selenium and arsenic alloy with various concentrations of the arsenic. In this work, x-ray photoconductor using amorphous selenium alloyed with arsenic were fabricated with different concentrations of the arsenic (0.1 wt.%, 0.3wt.%, 0.5wt.%, 1wt.%, 1.5wt.%, 3wt.%, 5wt.%). The seven kind of samples was fabricated with a-Se alloyed with arsenic through vacuum thermal evaporation. We also investigate the arsenic concentration dependence on the device performance in radiation detector. The electric characteristics of radiation detector devices with changing additive ratio of the arsenic is performed by measuring the x-ray induced photocurrent and integrating it over time to find the total charge. The thickness of a-Se is $100{\mu}m$. Bias voltages $3V/{\mu}m$, $6V/{\mu}m$， $9V/{\mu}m$ are applied at the samples. As results, the net charge of a-Se 0.3% As sample is $526.0pC/mR/cm^2$ at $9V/{\mu}m$ bias. The net charge is decreased as with the increasing additive ratio of arsenic.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 센서 박막재료 반도체재료 기술교육
• /
• pp.27-30
• /
• 2002

Photoconductor for direct detection flat-panel imager present a great materials challenge, since their requirements include high X -ray absorption, ionization and charge collection, low leakage current and large area deposition. Selenium is practical material. But it needs high thickness and high voltage in selenium for high ionization rate. We report comparative studies of detector sensitivity. One is an a-Se with $70{\mu}m$ thickness on glass. The other has hybrid layer of depositting ZnS phosphor with $100{\mu}m$ on a-Se. The leakage current of hybrid is similar to it of a-Se, but photocurrent is lager than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.420-423
• /
• 2002

In recent years, there has been keen interest in developing f1at panel detectors for all modalities of radiology, including gerneral radiology, fluoroscopy(angiography and cardiology), electronic portal imaging, and mammography. In this paper, we report the new hybrid x-ray detector consisted of CsI(Tl) photoemission layer and a-Se photoconductor layer to resolve conventional x-ray detector such as the direct detector using a-Se and the indirect detector using CsI(Tl)/a-Si. To design the structure of CsI(Tl)/a-Se detector, the penetrated energy spectrum and absorption fraction was estimated using MCNP 4C code. Experimental results showed that the absorption fraction of $500{\mu}m-Se$ film and $150{\mu}m-CsI\left(Tl \right)/a-Se\left( 30{\mu}m \right)$ film is 70% at 70 kVp. The absorption energy is 90% at $350{\mu}m-CsI(Tl)$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
• /
• pp.388-391
• /
• 2003

The properties of these detectors can be controlled by electronics and exposure conditions. Flat-panel detectors for digital diagnostic imaging convert incident x-ray images to charge images. Flat panel detectors gain more interest real time medical x-ray imaging. Active area of flat panel detector is $14{\times}17$ inch. Detector is based on a $2560{\times}3072$ away of photoconductor and TFT pixels. X-ray conversion layer is deposited upper TFT array flat panel with a 500m by thermal deposition technology. Thickness uniformity of this layer is made of thickness control technology(5%) of thermal deposition system. Each $139m{\times}139m$ pixel is made of thin film transistor technology, a storage capacitor and charge collection electrode having geometrical fill factor of 86%. Using the separate driving system of two dimensional mosaic modules for large area, that is able to 4.2 second per frame. Imaging performance is suited for digital radiography imaging substitute by conventional radiography film system..

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.432-435
• /
• 2002

The ultimate study of this research is to improve the properties of digital X-ray receptor based on amorphous selenium. There are being two prominent studying for Digital Radiography. Direct and Indirect method of Digital Radiography are announced for producing high quality digital image. But each two systems have strength and weakness. This is a basic research for developing of Hybrid digital radiography which is a new type X-ray detector. ln this study, we investigated the electrical characteristic of multi-layer$(CaWO_4+a-Se)$ as a photoconductor according to the changing iodine composition ratio. The iodine composition ratio of a-Se compound is classified into 5 different kinds which have 30ppm, 100ppm, 300ppm, 500ppm, 700ppm and were made test sample throught thermo-evaporation. The phosphor layer of $CaWO_4$ was overlapped on a-Se using EFIRON optical adhesives. We measured the dark and photo current about the test sample and compared the electrical characteristic of the net charge and signal-to-noise ratio. Among other things, test sample of compound material of 700ppm iodine showed good characteristic of $2.53nA/cm^2$ dark current and $479nC/cm^2{\cdot}mR$ net charge at $3V/{\mu}m$.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
• /
• pp.436-439
• /
• 2002

Recently, It has performed that the basic research of the photoconductive material and the development and application of the digital radiograph detector which is divided into the direct and indirect method. The objective of this study investigate the effect of the electric characteristic about changing the composition of Arsenic in hybrid detector system for compensating a defect of conventional. We fabricated samples using the amorphous Selenium and Arsenic alloy with various concentrations of the Arsenic{seven step 0.1%, 0.3%, 0.5%, 1%, 1.5%, 3%, 5%). And using EFIRON optical adhesives the formed multi-layer$(Gd_{2}O_{2}S(Eu^{2+}))$ composed phosphor layer. X-ray and light sensitivity was measured to study x-ray response characteritics. As results, highest value was measured as output net charge and SNR were $315.7pC/cm^2/mR$ and 99.4 at 0.3%As doping ratio.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
• /
• pp.813-816
• /
• 2002

We investigate the junction between CdZnTe and a variety of metals with the aim of determining whether the choice of metal can improve the performance of X-ray image detectors, in particular minimizing the dark current. The samples consist of $5{\mu}m$ thick CdZnTe with top electrodes formed from In, Al, and Au. For each metal, current transients following application of valtages from -10V to 10V are measured for up to 1 hour. We find that dark currents depending on the metal used. The current is controlled by hole injection at the metal-CdZnTe junction and there is consistent trend with the metal's work function possibly and it seems that metal to CdZnTe layer junction is ohmic contact.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
• /
• pp.71-74
• /
• 2003

Photoconductor for direct detection fiat-panel imager present a great materials challenge, since their requirement include high X-ray absorption, ionization and charge collection, low leakage current and large area deposition, CdTe is practical material. We report studies of detector sensitivity, That is an CdTe with $5{\mu}m$ thickness on glass. That is hybrid layer of depositting ZnS:AgCl phosphor with $100{\mu}m$ on CdTe. The leakage current of hybrid is similar to it of a-Se, but photocurrent is larger than a-Se. Both of them have high spatial resolution, but hybrid has higher sensitivity than a-Se at comparable bias voltage.

• 한국방사선학회논문지
• /
• 제3권4호
• /
• pp.29-33
• /
• 2009

최근 디지털 방사선 영상획득을 위한 평판형 X선 검출기에 이용되는 광도전체(a-Se, $HgI_2$, PbO, CdTe, $PbI_2$ 등)에 대한 관심이 증대되고 있다. 본 연구에서는 $HgI_2$ 와 a-Se 필름 변환체에 대해 X선에 대한 전기적 신호검출 특성을 조사하였다. 수백 마이크로의 두꺼운 광도전체 필름 제작을 위해 $HgI_2$는 입자침전방법을 이용하였고, a-Se은 종래의 진공열증착법을 이용하였다. 제작된 시편에 대한 전기적 특성 실험은 누설전류, 신호응답 특성, 민감도 등을 측정하였다. 실험결과로부터, $HgI_2$는 상용화된 a-Se에 비해 낮은 동작전압특성과 우수한 신호 발생율을 보임을 알 수 있었다.

• 한국방사선학회논문지
• /
• 제10권8호
• /
• pp.565-569
• /
• 2016

최근 다엽콜리메이터를 부착한 선형가속기를 이용한 방사선수술의 빈도가 점차 높아지고 있다. 이러한 정교한 방사선 수술은 소조사면 내에 고선량의 방사선이 집중적으로 조사되기 때문에 체계적이고 정확한 정도관리가 필수적이다. 본 연구는 PIB(Particle in Binder) 방식 중 침전법을 이용하여 $400{\mu}m$ 두께의 요오드화납($PbI_2$)과 요오드화수은($HgI_2$) 광도전체 센서 시편를 제작하였다. 제작된 시편의 전기적 특성은 암전류, 출력전류, 응답특성 및 선형성을 평가하였다. 평가 결과, $HgI_2$ 가 우수한 신호발생량과 선형성을 보였다. 끝으로, 두께에 따른 $HgI_2$ 센서의 신호반응 특성 결과, $400{\mu}m$ 두께에서 신호발생효율이 가장 높았고, ${\pm}2.5%$ 이내의 우수한 재현성을 보였다.