Editing Selenium (section)

===Photoconductors===
Amorphous selenium (α-Se) thin films have found application as photoconductors in [[flat-panel detector|flat-panel X-ray detectors]]. These detectors use amorphous selenium to capture and convert incident X-ray photons directly into electric charge. Selenium has been chosen for this application among other semiconductors owing to a combination of its favorable technological and physical properties:<ref name=r1>{{cite journal|doi=10.1109/JSEN.2019.2950319|title=Recent Developments of Amorphous Selenium-Based X-Ray Detectors: A Review |year=2020 |last1=Huang |first1=Heyuan |last2=Abbaszadeh |first2=Shiva |journal=IEEE Sensors Journal |volume=20 |issue=4 |pages=1694–1704 |bibcode=2020ISenJ..20.1694H |s2cid=208833373 |doi-access=free }}</ref><ref name=r2>{{cite journal|doi=10.1002/pssb.200982007|title=Amorphous selenium and its alloys from early xeroradiography to high resolution X-ray image detectors and ultrasensitive imaging tubes |year=2009 |last1=Kasap |first1=Safa |last2=Frey |first2=Joel B. |last3=Belev |first3=George |last4=Tousignant |first4=Olivier |last5=Mani |first5=Habib |last6=Laperriere |first6=Luc |last7=Reznik |first7=Alla|author7-link=Alla Reznik |last8=Rowlands |first8=John A. |journal=Physica Status Solidi B |volume=246 |issue=8 |pages=1794–1805 |bibcode=2009PSSBR.246.1794K |s2cid=122848842 }}</ref>
# Amorphous selenium has a low melting point, high vapor pressure, and uniform structure. These three properties allow quick and easy deposition of large-area uniform films with a thickness up to 1&nbsp;mm at a rate of 1–5&nbsp;μm/min. Their uniformity and lack of grain boundaries, which are intrinsic to polycrystalline materials, improve the X-ray image quality. Meanwhile the large area is essential for scanning the human body or luggage items. 
# Selenium is less toxic than many compound semiconductors that contain arsenic or heavy metals such as mercury or lead.
# The mobility in applied electric field is sufficiently high both for electrons and holes, so that in a typical 0.2&nbsp;mm thick device, c. 98% of electrons and holes produced by X-rays are collected at the electrodes without being trapped by various defects. Consequently, device sensitivity is high, and its behavior is easy to describe by simple transport equations.