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Secondary-ion-mass spectroscopy (SIMS) analysis of insulators using positive primary beams is routinely performed by compensating the induced charge with a coincident electron beam. In the case of SIMS depth profiling, the established method consists of focusing an electron beam into the SIMS crater with a current well in excess of that of the primary ion beam. In this article we used both caesium and oxygen beams to bombard float glass, and intrinsic and doped diamond samples while varying the electron beam current and the area bombarded by electrons. We have studied how the electron beam to primary ion current density ratio modifies the charging conditions. We demonstrate that, for certain insulating and highly resistive materials, defocusing of the electron beam so as to cover the whole of the sample surface and part of the sample holder is extremely effective. It is also observed that the defocused electron beam works efficiently for an electron to primary ion current density ratio less than 1. We attribute this to the enhancement of surface conductivity through the creation of carriers in the conduction band, and observe similar effects when irradiating the surface with a laser diode. The ability to use a defocused electron beam will significantly aid profiling of insulating and highly resistive materials where alignment of the coincident electron and ion beams is problematic. Defocusing of the electron beam also offers the possible advantage of reducing or eliminating localized electron beam damage of certain material surfaces prior to and during profiling.

In recent years, the ability to grow single crystal layers of both doped and pure diamonds has improved, and devices for applications in high power electronics and microelectronics are being developed, most of them based on boron doped diamond. In this work, convoluted angular and energy spectra (so-called secondary ion mass spectrometry energy spectra) have been measured for B+11, C+12, O+16, CO+ and CO2+ ions ejected from a single crystal boron doped diamond layer under ultralow energy oxygen and electron beam bombardment. A low energy tail was observed in the C+12, CO+, and CO2+ signals, corresponding to ions produced in the gas phase. Changing the bombardment conditions, we have identified interaction with the electron beam as the main ionization mechanism. In the case of C+12 it appears that the gas phase ions are produced by electron stimulated desorption and postionization of surface species created by the oxygen beam. We have detected high signals for CO+ and CO2+ ionized in the gas phase, which supports a mechanism previously suggested to explain the anomalously fast diamond erosion under oxygen ion beam bombardment. We also observe that some species appearing in the mass spectrum are produced by electron stimulated desorption and this needs to be remembered when analyzing these on insulating diamond with charge compensation.

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The primary beam energy and species (Cs+, Ar+) dependence of ultra low energy SIMS depth profiles of ultra‐shallow boron implants into CVD grown diamond is investigated in this paper. The data are compared with TRIM simulation of the 5 keV 11B+ implant. Cs+ profiles (1 keV, 30°) appear to be seriously distorted by atomic mixing and recoil implantation due to the high mass of the probe. Ar+ profiles (300 eV–1 keV, 0°) are less distorted, but both Cs+ and Ar+ tend to produce significant tails. The Ar+ SIMS profiles produce implants which appear to be shallower than the TRIM simulation. We show that profiling using Ar+ with energies between 0.3 and 1 keV can be used to extrapolate a profile to zero beam energy. The extrapolated data indicate a centroid between 5 and 10 nm from the surface, whereas TRIM predicts 11 nm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)