P. Bergonzo et al., Optimising CVD diamond properties for radiation detection applications: Growth conditions, defects, and uniformity, NEW DIAM FR, 11(2), 2001, pp. 113-128
CVD diamond is a remarkable material for the fabrication of radiation detec
tors. The radiation hardness, chemical resistance and high-temperature oper
ation capabilities of diamond motivate its use for the fabrication of devic
es operating in hostile environments such as those encountered in the nucle
ar industry and high-energy physics. For this purpose. we have frown polycr
ystalline diamond films using the microwave plasma enhanced chemical vapour
deposition technique (CVD). Deposition processes were optimised according
to the application requirements. This includes the synthesis of films with
high sensitivity or with short carrier lifetime. Defect level influence on
the detection characteristics were studied : they may be the cause of an ob
served instability of the device responses. We have found, however, that it
is possible to moderate these trends through the fine-tuning of the growth
conditions and of the device preparation steps. Films with thicknesses ran
ging from 5 to 500 mum have been used for detector fabrication. Using a mic
rometer-size focused X-ray beam, we have also studied the nonuniformity of
devices fabricated from polycrystalline diamond. Sensitivity maps were imag
ed and correlated with the grain structure. We present here recent developm
ents studied at CEA in Saclay for material optimisation for specific applic
ations, including radiation hard counters, X-ray intensity, shape and beam
position monitors, solar blind photodetectors, and high dose rate gamma-met
ers.