Deep UV, visible blind, photoconductive devices fabricated on polycrystalli
ne CVD diamond using inter-digitated planar electrodes have shown promising
characteristics. The 'as-fabricated' device performance is insufficient fo
r many applications; a particularly demanding example is the monitoring of
high power excimer lasers operating in the UV, which ideally require visibl
e-blind, radiation hard fast UV detectors. However, post-growth treatments
can strongly modify the performance level achieved. In this paper, we show
that sequentially applied treatments can progressively change both the gain
and speed of these devices. We have used charge sensitive deep level trans
ient spectroscopy (Q-DLTS) to study the effect of these treatments on the d
efect structure of CVD material. For the first time, we report the realisat
ion of diamond photoconductive devices capable of operating at more than 1
MHz at 193 nm.