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Scanning ion beam microscopy : a new tool for mapping the transport properties of semiconductors and insulators

Proton microbeams of energy from 3 to 5 MeV have been used to investigate cross section of Si, CdTe and CVD diamond samples by recording the charge pulses delivered at the electrodes by the single proton with a charge-sensitive electronic chain. The investigated depth varies from 50 to 140 mm depending on the proton energy and on the material. In the case of an homogeneous material (Si, CdTe), lifetime and mobility values can be obtained, together with the in-depth electrical field profiles. For polycrystalline materials, the maps of collection efficiency can be correlated with morphological maps putting in evidence a columnar-like structure due to the film growth mechanism. In these cases, it is relatively difficult to separate the effects due to the electrical field from the carrier transport properties (mobility, lifetime). Anyway, maps of collection length are quite important in order to detect the electrical inhomogeneities of polycrystalline materials.

scanning ion beam; proton microbeams; IBIC microprobe; materials

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