  We explore the possibility to improve the performance of 0.5 cm thick Cadmium
Zinc Telluride (CZT) detectors with the help of steering grids on the anode
side of the detectors. Steering grids can improve the energy resolution of CZT
detectors by enhancing the small pixel effect; furthermore, they can increase
their detection efficiency by steering electrons to the anode pixels which
otherwise would drift to the area between pixels. Previously, the benefit of
steering grids had been compromised by additional noise associated with
currents between the steering grids and the anode pixels. We use thin film
deposition techniques to isolate the steering grid from the CZT substrate by a
150 nm thick layer of the isolator Aluminiumoxide. While the thin layer does
not affect the beneficial effect of the steering grid on the weighting
potentials and the electric field inside the detector, it suppresses the
currents between the steering grid and the anode pixels. In this contribution,
we present first results from a 2 x 2 x 0.5 cm CZT detector with 8 x 8 pixels
that we tested before and after deposition of an isolated steering grid. The
steering grid improves the 662 keV energy resolution of the detector by a
factor of 1.3 (from about 2% to about 1.5%), while not reducing the detection
efficiency. To gain further insights into the detector response in the region
between pixels, we measured energy spectra with a collimated Cs137 source. The
collimator measurements can be used to enhance our understanding of energy
spectra measured under flood illumination of the detectors.
