Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and AsxSe1−x

Yu, Tung‐Yuan; Pan, Fu‐Ming; Chang, Chieh-Ming J.; Lin, Jian-Siang; Huang, Wen Chang

doi:10.1063/1.4927740

Cited by 10 publications

(4 citation statements)

References 23 publications

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“…The darker color property of the polycrystalline Se (p-Se) is due to the strong optical absorptions in the visible range of long wavelengths [13], which will also be evidenced in the transmittance analysis section. It can be seen that the crystallization temperature at 62 °C for a-Se thin films is higher than for those of a-Se thick films [11,12], which is attributed to the significant influence from substrate surface. Specifically, these Se atoms on the substrate surface are hard to migrate to grow into a crystal core, because of the bondage of the substrate surface, which will exert more serious effects on the thinner a-Se films than the thicker a-Se films.…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, several reports have preferred to investigate the a-Se thick films with a thickness of tens of microns to hundreds of microns [4,5,6,7,10], since a-Se thick films can absorb more X-ray energy and thus produce a higher photocurrent; further, the systematic research on the a-Se thin films with the thickness of a few microns is rare [8]. Nevertheless, the low crystallization temperature, 40–50 °C, is a fatal disadvantage of a-Se thick films, as it seriously restricts its practical applications [11,12]. Theoretically, a-Se thin films possess the higher crystallization temperature, resulted from that the astrict of substrate hinders the migrations of atoms.…”

Section: Introductionmentioning

confidence: 99%

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Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Zhu

Yang

et al. 2018

Materials

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Amorphous selenium (a-Se) thin films with a thickness of 1200 nm were successfully fabricated by thermal evaporation at a low vacuum degree of 10−2 Pa. The structural properties involving phase and morphology showed that a-Se thin films could be resistant to 60 °C in air. Also, a transformation to polycrystalline Selenium (p-Se) was shown as the annealing temperature rose to 62 °C and 65 °C, with obvious changes in color and surface morphology. Moreover, as the a-Se transformed to p-Se, the samples’ transmittance decreased significantly, and the band gap declined dramatically from 2.15 eV to 1.92 eV. Finally, the X-radiation response of a-Se was investigated as an important property, revealing there is a remarkable response speed of photogeneration current both X-ray on and X-ray off, with a requirement of only a very small electrical field.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Zhu

Yang

et al. 2018

Materials

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“…然而, 非晶硒的玻璃化转变温度约为320 K, 略高于室温 [2,8] . 作为光电转换器件, 当光照作用使非晶硒温度升高时, 有可能引起结构弛豫甚至结晶, 致其光电性能劣化 [9,10] . 为此人们通过掺杂As和Te等元素提高非晶硒的稳定性, 如 X射线平板探测器使用掺杂了质量分数为0.3%-0.5% As的非晶硒 [10−13] .…”

Section: 引言unclassified

Mechanism of rapid compression-induced melt crystallization in selenium

Wang,

et al. 2021

Acta Phys. Sin.

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Amorphous selenium (Se) can be easily prepared by quenching the melt, which indicates that the Se possesses the good glass-forming ability. However, crystallization occurs after rapidly compressing the melt within about 20 ms. In this work, we investigate the mechanism of rapid compression-induced crystallization from Se melt. Compressing Se melt experiments are carried out at the following temperatures: 513, 523 and 533 K. The melt is rapidly compressed under 2.4 GPa for about 20 ms. Different holding times, i.e. 0, 30, 60 min after solidification are adopted. The samples are quenched to room temperature and then unloaded to ambient pressure. The X-ray diffraction analysis of the recovered sample indicates that the crystallization product is the t-Se. It is found that with the prolongation of holding time, the grain size increases due to the continuous aggregation growth of crystal grains. By comparing with the isothermal crystallization products of amorphous Se and ultrafine Se powder, it is suggested that the rapid compression-induced solidification product should be t-Se crystalline. The speculation that the solidification product is amorphous Se and it crystallizes in the cooling process does not hold true. The amorphous Se cannot be prepared through the rapid compression process on a millisecond scale. It is related to the thermal stability of amorphous Se under high pressure. It is reported that the dependence of crystallization temperature Tx on pressure i.e. dTx/dP for amorphous Se is about 40–50 K/GPa in a range of 0.1 MPa–1 GPa. However, the Tx of amorphous Se is almost constant in a range of 2–6 GPa. It means that the thermal stability of amorphous Se against crystallization does not increase with increasing pressure after 2 GPa. In this work, the temperature of 513–533 K in the experiments is higher than the Tx of amorphous Se. Therefore, the t-Se crystal is the stable phase and amorphous Se is unstable. The Se melt tends to crystallize in the supercooled liquid state after rapid compression. It is interesting to investigate the mechanism of dTx/dP curve discontinuous change at around 2 GPa in the future. Both the Se melt after rapid compression and the amorphous Se before crystallization are in supercooled liquid state. We speculate that high pressure may result in the microstructure transition in supercooled liquid state Se.

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“…Apart from this, selenium is used as a material in electro-photography [14], x-ray photoconductors [15], high-definition digital video cameras [16], pigments [17], semiconductors [18], filament detector arrays [19], medical imaging sensors [20], to improve the thermal stability of photosensors [21], optical applications in the IR region [22], photonic devices [23], and superconductors [24].…”

Section: Introductionmentioning

confidence: 99%

Impact of Thickness on the Optical Properties of Selenium Thin Films

Udachan¹,

Ayachit²,

Udachan

et al. 2021

IyU

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Objectives: The primary objective of this investigation is to make a systematic study on the impact of thickness on optical properties, such as energy gap, absorption coefficient, optical density etc., for selenium thin films. Understanding of the band gap energy and its influence on film thickness is of utmost importance in acquiring the intended electrical characterization of semiconducting films. Materials and methods: Ultra-purity selenium (99.99 %) was deposited on glass substrates. During deposition, the glass substrate with its holder were rotated with constant speed to have a smooth coating. Results and discussions: The XRD findings indicate that selenium is amorphous in nature. The optical band gap energy is found to be decreasing form (2.3 to 2eV) with the rise of film thickness in interval (200 to 1000 nm). The band gap energy obeys inverse square law with respect to thickness. Conclusion: We have properly grown thin films of Se below the De Broglie wavelength limit by thermal evaporation in vacuum. The optical density varies directly with film thickness. The absorption coefficients were in the interval (0.5 to 4) × 107m-1. The AFM results confirmed that the Se nano-size increases with the increase in thickness. Both the grain boundaries and sub-grain regions are clearly visible in the SEM micrographs

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Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and AsxSe1−x

Cited by 10 publications

References 23 publications

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Mechanism of rapid compression-induced melt crystallization in selenium

Impact of Thickness on the Optical Properties of Selenium Thin Films

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