G. Holmén

Radiation enhanced annealing of radiation damage in Ge

Abstract Ge (110) single crystals heated to a temperature of 228°C have been bombardment disordered by 40 keV ions at a dose rate of 6 × 1011 ions/cm2 sec. The enhanced annealing caused by 40 keV Ge ions at a dose rate of 6 × 1011ions/cm2 sec was studied as a function of dose by measuring the secondary electron yield. The depth distribution of damage was determined by the channeling technique using 500 keV He ions. It is shown that enhanced annealing occurs at the inner part of the damage region and proceeds outwards towards the crystal surface. The dose necessary to completely anneal a disordered layer is about 3.0 × 1015 ions/cm2. A model for the annealing process is discussed. The maximum path length of the secondary electrons emitted from Ge during the bombardment with 40 keV Ge ions has been determined to be equal to approximately 40 A.

A study of the production and removal of radiation defects in Ge using secondary electron emission

Abstract The production and removal of radiation defects in Ge (110) single crystals are studied by measuring the variation in the kinetic secondary electron emission yield during bombardment by 40 keV Ge ions. A strong dose rate effect has been found in the temperature dependence of the defect production. An activation energy of 1.44 eV has been calculated for the defect which plays an important role in the removal of damage in Ge.

Influence of energy transfer in nuclear collisions on the ion beam annealing of amorphous layers in silicon

Amorphous surface layers produced by ion bombardment in silicon on sapphire have been ion beam annealed at 300u2009°C. The annealing behavior has been found to be dependent on the part of the ion energy transferred in nuclear collisions.

Radiation damage in Ge produced by noble gas ions investigated by the secondary electron emission method

Abstract 40 keV Ne, A, Kr and Xe ions have been used to bombard Ge single crystals at perpendicular incidence to (110) under clean target conditions. The temperature, dose and dose rate dependences of the accumulation of disorder have been determined. In a low temperature interval, 50–150°C, small temperature and dose rate effects on the accumulation of disorder were detected for Ne and A but for the other ions there was no such dependence. At temperatures above 150°C the temperature and dose rate for all types of ions used influence the accumulation of disorder. Different temperatures for the transition from a crystalline to a disordered region were detected for the various dose rates and ions used. Activation energies of 1.45 ± 0.15 eV for the observed defects have been calculated.

Radiation damage in Ge produced and removed by energetic Ge ions

Abstract Single crystals of Ge (110) were bombarded by 40 keV Ge ions at a dose rate of 6.0 × 1013 ions/cm2 sec in the temperature region 50–500°C. The secondary electron emission yield was used to study the state of disorder. In accordance with Chaddertons damage center nucleation model the growth of disorder can be divided into several dose intervals. Radiation enhanced and thermal annealing characteristics have also been studied using a probe ion beam of dose rate 6.0 × 1011 ions/cm2 sec. Evidence for both bombardment enhanced and thermal annealing are established. The bombardment enhanced annealing of a continuous disordered layer occurs at the inner region of the layer. The temperature dependence of the bombardment enhanced annealing indicates that a thermal step is included in the annealing process.

Self-sputtering of ge single crystals

Abstract Temperature dependence of self-sputtering in germanium has been determined for the Ge (110), Ge (111) and Ge (100) surfaces. At room temperature the sputtering yield is 8 atoms/ion for all three surfaces bombarded by 50 keV Ge ions. At about 300°C the yield drops to 2.5 atoms/ion for the Ge (110) and Ge (111) surfaces and 2.9 atoms/ion for the Ge (100). The transition is caused by a change in the crystal order. A comparison with current sputtering theories is made.

Ion beam induced oxidation of silicon

A new physical phenomenon causing oxidation of silicon has been observed. The phenomenon is controlled by the impact of an energetic ion beam on a clean silicon target exposed to low‐pressure oxygen. An oxide layer of 50–100 A can be formed at room temperature by properly choosing the oxidation conditions. The growth was studied in situ by measuring the ion‐induced secondary electron yield. A strong dependence on oxygen pressure and target temperature was observed. By studying the oxide with x‐ray photoelectron spectroscopy, it was concluded that the film formed is stoichiometric SiO2 . A discussion on possible growth mechanisms is carried out in terms of ion energy deposition.

Properties of ultrahigh vacuum self‐implantation‐induced amorphous germanium

Geu2009(111) was self‐implanted in ultrahigh vacuum to prepare an impurity‐free amorphous layer. The same extraordinary amorphous state of Ge was induced as that found earlier with 121Sb+ implantation in normal vacuum. This eliminates the possibility that this anomalous a‐Ge is impurity stabilized.

Electrical measurements of boron implanted silicon on sapphire and bulk silicon

Abstract Hall effect and sheet resistivity measurements have been performed on boron implantations in 1μm silicon layers on sapphire (SOS), and in bulk silicon. The doses used were 1014, 1015 and 1016 ions/cm2, and implantation energies were 150 and 300 keV. The samples were annealed at temperatures between 300 and 800°C. As a rule the effective number of carriers in SOS was found to be about twice the number of carriers in bulk silicon. However, the mobility is lower in bulk silicon, resulting in a sheet resistivity almost the same in boron implanted SOS and bulk silicon.

CW laser annealing of boron implanted polycrystalline silicon

Abstract The electrical characteristics have been measured on CW laser annealed boron implanted polycrystalline silicon layers. It is shown, that a resistivity can be obtained, which is only about double that of a single crystalline layer doped to the same level. By appropriate choice of doping and laser annealing parameters, a temperature coefficient close to zero can be achieved. It is also shown that laser irradiation can be used to trim a furnace annealed polysilicon resistor to a desired resistance value.