Highly-Sensitive Polycrystalline Diamond X-Ray Dosimeter With Hydrogen Termination Contacts

This letter reports the polycrystalline diamond (PCD) dosimeter with near ideal linearity and high sensitivity to meet the application requirements of medical X-ray dose measurement for low cost, large size, and high performance. The device is fabricated by using hydrogen termination modulation ohmic contact and high-quality materials with preferred (111) and (311) crystal orientation, large grain size and low impurity content. The linearity, specific sensitivity, and current gain obtained from experimental measurements are 0.999, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.482~\mu $ </tex-math></inline-formula>C<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula>Gy<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}\cdot $ </tex-math></inline-formula>mm<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{3}}$ </tex-math></inline-formula> and 5.76 at 300 V (1 V/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m), respectively. Furthermore, the signal-to-noise ratio that meets the requirements of International Atomic Energy Agency is greater than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{4}}$ </tex-math></inline-formula> at 5 to 300 V, and the current fluctuations under dynamic voltage switch test condition of more than 30 cycle (2 s on-state and 1 s off-state) is only 0.241% at 200 V under dose rate of 6.184 Gy/min. This study indicates that PCD dosimeter fabricated by optimizing contact structure and material properties has a great potential for medical dose measurement.