Evaluation of a structured cesium iodide film for radiation imaging purposes

Tao, Jinhui; Goodman, C.A.; Cho, G.; Drewery, J.; Hong, Won G.; Lee, H.; Kaplan, S.N.; Mireshghi, A.; Perez‐Mendez, V.; Wildermuth, D.

doi:10.1109/nssmic.1993.373619

Cited by 3 publications

(5 citation statements)

References 16 publications

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“…& 1 -= g ( r , t ) -R p ( r y t ) + -V~J p , dt 4 (3.36) (3.37) where g(r,t) is the electron hole pair generation. n(r,t) and p(ryt) are the electron and hole densities respectively, Rn(r,t) and Rp(r,t) are the electron and hole reduction rates, respectively, caused by trapping on deep level impurities, q is the electron charge, and Jn(r,t) and Jp(r,t) are the electron and hole current densities respectively.…”

Section: Photoconductor Transient Parametersmentioning

confidence: 99%

“…(2) The second possibility is to use the scintillator/a-Si:H thin photodiode structure. (3) using the a-Si:H photoconductor instead of the photodiode in order to increase the sensitivity of the detector [4]. In later sections, we will demonstrate the capability for detecting minimum ionizing electrons based on the last two configurations.…”

Section: Fluorescence Decay Timementioning

confidence: 99%

“…In most applications of position-sensitive radiation detection, conventional radiography[l-31, and digital radiography [4][5][6], a scintillator screen is used to convert the incoming radiation into Visible light which is then detected on film or other position sensing device. Such scintillators are usually required to have high spatial resolution and high output brightness characteristics.…”

Section: Introductionmentioning

confidence: 99%

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High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

Tao

1995

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Section: Photoconductor Transient Parametersmentioning

confidence: 99%

Section: Fluorescence Decay Timementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

Tao

1995

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“…It has been used in products such as solar cells [1], thin film transistor liquid crystal displays (TFT LCDs) and diodes [2]. Amorphous silicon photodiodes have also been used for imaging devices, such as linear image sensors for facsimile and scanners [3,4], and two-dimensional arrays for medical imaging and high-energy particles detection, such as Xand gamma-ray detectors [5][6][7][8][9][10]. Unlike crystalline Si, whose absorption maximum is in the infrared part of the spectrum, a-Si:H has the highest photoconductivity in the visible red region, which makes it an ideal material for many photoelectrical applications using a red visible light source.…”

Section: Introductionmentioning

confidence: 99%

Effect of long-term He–Ne laser light exposure and subsequent annealing on hydrogenated amorphous silicon pin photodiodes

Ristova

Kuo

Lee

et al. 2005

Semicond. Sci. Technol.

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Changes in the current-voltage (IV) characteristics were monitored on as prepared a-Si:H pin photodiodes during 60 min He-Ne laser illumination (every 15 min in situ measurements). After illumination was over, the pin diodes were subjected to 1 h annealing at 200 • C and IVs were taken again. Results showed that the short circuit current (I sc ) decreased with the He-Ne exposure time which is known as a Stabler-Wronski effect of degradation and increased after the annealing. In order to describe the origin of this phenomenon, a 1 µm thick a-Si:H film was deposited on Mo-coated glass sheets by plasma enhanced chemical vapour deposition (PECVD) using the same procedure as that of the i-type layer in the pin diodes. Fourier transform infrared spectra (FTIR) were taken on the sample before and after the 1 h He-Ne laser exposure as well as after annealing for 1 h at 200 • C in air. Hydrogen (H) concentration in the film was estimated from the typical Si-H vibration absorbance peak at 2000 cm −1 . The results showed that the H-concentration decreases from the initial value of about 10%, to about 7% after the 1 h He-Ne laser exposure. After the thermal annealing, the hydrogen concentration increased to about 9%. The above hydrogen concentration change was directly related to the change in the IV characteristics of the pin a-Si:H diode.

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“…Amorphous silicon photodiodes have been used for a variety of imaging devices, such as linear image sensors for facsimile and scanners [1,2], and two-dimensional arrays for medical imaging and high-energy particle detection, such as x-and gamma-ray detectors [3][4][5][6][7][8]. In our previous studies, we found that a-Si:H has the highest photoconductivity in the visible red region, which makes a-Si:H photodiodes convenient for red visible light detection.…”

Section: Introductionmentioning

confidence: 99%

Influence of the roughness of molybdenum back electrode on the photodiode characteristics under He–Ne illumination

Ristova

Kuo

Lee

2003

Semicond. Sci. Technol.

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Molybdenum thin films, about 300 nm thick, were RF sputtered on silicon wafers used as a substrate, in order to produce thin film diode back electrodes. The Mo films were treated with reactive ion etching (RIE) for different times (20 s, 40 s, 60 s and 120 s), producing surfaces with different degrees of roughness. Atomic force microscopy (AFM) showed a pyramidal structure of the etched surfaces. It was found that the roughness is strongly related to the RIE time. The change of the reflection coefficient of the etched Mo surfaces was measured with respect to the non-etched (as-is) Mo surface. The results showed dependence of the relative change of the surface reflection with the RIE time. Such prepared molybdenum surfaces of different roughness were used as back electrodes for preparation of hydrogenated amorphous silicon p-i-n diodes, prepared by the plasma-enhanced chemical vapour deposition method (PECVD). Molybdenum coating (150 nm thick) by RF sputtering was also used to produce top electrodes. The final diode structure was Mo/p-i-n/Mo. The grid structure of the top electrode was produced by a photolithography technique. Thirteen various front electrode grid patterns were designed to permit the He-Ne laser beam spot of 7 mW and about 0.7 mm cross-section. The laser beam penetrated through the p-i-n structure, covering the entire diode active area. The short circuit current (I sc ) was measured for 13 diode grid shapes of each sample, including the diodes on the flat (untreated) back Mo electrode. The results showed that the average I sc depends on the RIE time. The dark and He-Ne light characteristics showed changes with the RIE time. From the measured IV characteristics, the serial resistance (R s ) was found to increase with the RIE time, except for the 20 s treated RIE sample. Results of I sc and R s suggested that, besides the light scattering mechanism resulting from the surface roughness, there is another contributing factor to the photodiode performance enhancement, and that is the surface of the pi junction; the greater the roughness, the larger the junction area.

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Evaluation of a structured cesium iodide film for radiation imaging purposes

Cited by 3 publications

References 16 publications

High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

High spatial resolution radiation detectors based on hydrogenated amorphous silicon and scintillator

Effect of long-term He–Ne laser light exposure and subsequent annealing on hydrogenated amorphous silicon pin photodiodes

Influence of the roughness of molybdenum back electrode on the photodiode characteristics under He–Ne illumination

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