In a program of developing radiation-hard silicon sensors for the LHC-ATLAS
experiment. we have irradiated various types of silicon sensors with 12 Ge
V protons at KEK. Among the other properties, we made a comparative study o
f characteristics of the sensors with two wafer planes <1 1 1 > and <1 0 0
>. The studied sensors are p-on-n type, which satisfy the ATLAS-SCT specifi
cations. Possible dependence on the substrate orientation could result from
different dangling-bond configurations, The compared characteristics are t
he charge collection efficiency, interstrip capacitance, and noise levels.
The noise levels were measured with a real ATLAS-SCT electronics system. A
substantial difference is observed in the interstrip capacitance at similar
to 10 kHz, while the difference is small at > 1 MHz, The differences in th
e charge collection efficiency and in the noise levels appear to be small.
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