Sensitive direct-conversion X-ray detectors formed by ZnO nanowire field emitters and β-Ga<sub>2</sub>O<sub>3</sub> photoconductor targets with an electron bombardment induced photoconductivity mechanism
Zhipeng Zhang, Manni Chen, Xinpeng Bai, Kai Wang, Huanjun Chen, Shaozhi Deng, Jun Chen
Abstract
Sensitive X-ray detection is needed in diverse areas motivated by a common desire to reduce radiation dose. Cold cathode X-ray detectors operating with a photoelectron multiplication mechanism called electron bombardment induced photoconductivity (EBIPC) have emerged as promising candidates for low-dose X-ray detection. Herein, the cold cathode detectors formed by ZnO nanowire field emitters and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mi mathvariant="normal">β</mml:mi> <mml:mtext>-</mml:mtext> <mml:msub> <mml:mrow> <mml:mi>Ga</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:mrow> </mml:math> photoconductor targets were proposed for sensitive direct-conversion X-ray detection. The charge carrier transport mechanism of EBIPC effect in X-ray detectors was investigated to achieve a high internal gain ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mn>2.9</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> ) and high detection sensitivity ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mn>3.0</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mn>3</mml:mn> </mml:msup> <mml:mtext> </mml:mtext> <mml:msubsup> <mml:mrow> <mml:mi>μCGy</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>air</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msubsup> <mml:mtext> </mml:mtext> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ) for a 6 keV X-ray at the electric field of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m4"> <mml:mrow> <mml:mn>22.5</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">V</mml:mi> <mml:mtext> </mml:mtext> <mml:msup> <mml:mi>μm</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . Furthermore, the proposed X-ray detectors showed the features of fast response time (40 ms), long-term stability (0.6% for 1 h), and low detection limit ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m5"> <mml:mrow> <mml:mn>0.28</mml:mn> <mml:mtext> </mml:mtext> <mml:msub> <mml:mrow> <mml:mi>mGy</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>air</mml:mi> </mml:mrow> </mml:msub> <mml:mtext> </mml:mtext> <mml:msup> <mml:mi mathvariant="normal">s</mml:mi> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ), suggesting that the direct-conversion cold cathode X-ray detectors are ideal candidates for low-energy X-ray detecting and imaging applications.