C.N. Waddell

Effects of thermal annealing on the refractive index of amorphous silicon produced by ion implantation

Precise infrared reflection measurements of the refractive index of silicon show that there are two well‐defined optical states of amorphous silicon produced by ion implantation. One is the as‐implanted amorphous state which is the high refractive index state produced by high fluence implantation of Si or P ions into Si samples. The other state, which has a refractive index intermediate between the as‐implanted and crystalline values, is induced by thermal annealing and is thermally stable until epitaxial recrystallization occurs.

High‐fluence implantations of silicon: Layer thickness and refractive indices

Refractive‐index measurements are given for amorphous Si produced by ion implantation. Reflection interference measurements in the frequency range 250≲ν≲ 7600 cm−1 were made for several Si samples implanted with P‐ion fluences between 1.0×1016 and 10×1016 ions/cm2 and ion energies between 0.20 and 2.7 MeV and for Si implants of 1.0×1016 and 3.0×1016 ions/cm2 and an ion energy of 0.30 MeV. The interference measurements were computer analyzed by using a model in which the damaged layer has a refractive index nD and extinction coefficient kD, and the substrate has a refractive index ns and ks=0. The optical constants of the two regions are smoothly connected by a transition region approximated by a half‐Gaussian curve of standard deviation σD. The finite‐width transition region is necessary for fitting the data. Excellent fits are obtained for literature values of ns and kD with the chi‐square being ?10−5. The value of kD has little effect on the analysis. Within the experimental accuracy a single curve for ...

Electrical and structural characterization of implantation doped silicon by infrared reflection

Abstract A physical model is presented for calculating infrared reflection interference spectra from ion implanted and annealed crystalline materials. The utility of the method is illustrated by presenting best fit spectra for a silicon sample implanted with 2.7 MeV phosphorous to a fluence of 1.74 × 1016 ions/cm2 and isothermally annealed at 500°C. Non-linear least-squares fitting of reflection data yields structural and electrical information about the implanted region with reasonable precision. The physical quantities determined are (i) the depth of the amorphous layer produced by implantation both before and during isothermal annealing, the thickness of the recrystallized material, and the widths of any transition regions, (ii) the dielectric properties of the amorphous and recrystallized material, and (iii) the characteristics of the free carrier plasma which yield the carrier density profile, the mobility near the carrier density maximum, and the carrier activation efficiency. Up to nine fitti...

The nuclear reaction efficiency correction for silicon and germanium detectors

Abstract The proton total-reaction cross section of silicon has been measured to be 732 ±20mb at 28 ±1MeV. The efficiency corrections for nuclear reactions in silicon and germanium detectors for protons from 5 to 150 MeV have been calculated using the energy dependence of the proton total-reaction cross sections. These calculations are shown to be in excellent agreement with direct measurements of the efficiency of silicon detectors.

Amorphous silicon produced by ion implantation: Effects of ion mass and thermal annealing

Characterization of the two optical states of amorphous Si produced by ion implantation is extended to include electron paramagnetic resonance, fundamental absorption edge, and density measurements in addition to infrared reflection. It is found that the properties of the two a‐Si states are not dependent upon the mass of the incident ion (12C, 29Si, 31P, 120Sn) or upon the anneal temperature for 400 °≤TA≤600 °C. The dangling‐bond density drops about a factor of 2 when the a‐Si makes a transition between the two states. The absorption coefficient also drops by more than a factor of 5, but the density of the a‐Si does not change when the transition occurs. The transition between states was not completed at TA=300 °C, so the annealing mechanism may be temperature dependent.

Total reaction cross sections for 29 MeV protons

Abstract The USC proton linear accelerator is being used in a programme of measuring the energy dependence of proton total reaction cross sections. As a first step in this programme measurements were made using the full beam energy. The anticoincidence beam attenuation technique was used. The following cross sections were obtained for 29 MeV protons: C, 418 ± 18 mb; Al, 775± 37 mb; 1023 ± 40 mbAg, 1471 ± 71 mb; and Au, 2209 ± 118 mb. These cross sections are compared to other measurements and optical model analyses.

Infrared studies of isothermal annealing of ion‐implanted silicon: Refractive indices, regrowth rates, and carrier profiles

A model‐dependent computer analysis technique developed previously has in this work been applied to the infrared reflection data of a number of 〈111〉 and 〈100〉 oriented Si samples which were implanted with high fluences of Si or P ions and then taken through an isothermal annealing process. The physical properties deduced from this analysis are: (i) Dielectric properties including the frequency dependent refractive indices of the recrystallized Si and of the a‐Si as a function of annealing temperature and time; (ii) structural information including the amorphous layer depth, widths of transition regions, the epitaxial regrowth rates; and (iii) electrical properties including the depth profile of the carrier density, the carrier mobility near the maximum carrier density, and the carrier activation efficiency. The physical interpretation of the results is discussed and, where possible, comparisons with results of other experiments are made.

THE ELASTIC AND INELASTIC SCATTERING OF 30.3 Mev PROTONS BY Si

Abstract The differential cross sections for the scattering of 30.3 MeV protons by the ground state and the first excited state of Si have been measured from 15° to 150° in the centre of mass. The elastic scattering has been analysed using the diffuse-surface optical model of the nucleus. Both the elastic and inelastic scattering angular distributions have been analysed using the generalized (“coupled-channel”) optical model of Buck. The inelastic scattering angular distribution is also compared to distorted-wave calculations.

PROTON TOTAL REACTION CROSS SECTIONS OF CARBON FROM 16 to 28 Mev

Abstract Optical model analysis of the elastic scattering of 18 to 31 MeV protons from carbon has shown that fairly wide variations in the optical model parameters are necessary to reproduce the data. A later analysis of these data in which it was assumed that the scattering amplitude is described by the sum of optical model and Breit-Wigner terms has indicated possible resonances at 19.8, 20.01, and 24.9 MeV (c.m.). The later analysis predicts an inflection point in the proton total reaction cross section at about 21 MeV (lab). In this work the reaction cross sections were measured in the energy range 16 to 28 MeV using the anti-coincidence beam attenuation technique, and the energy variation was achieved with beryllium absorbers and subsequent magnetic analysis. The measured reaction cross section agrees well with the cross section predicted by the later analysis except that there is a weak maximum instead of an inflection point at about 21 MeV (lab).

Design and performance of an 8 cm thick intrinsic germanium detector telescope

Abstract A detector telescope consisting of eight 1 cm thick intrinsic Ge diodes is described. The diodes have thin dead layer Li junctions (∼15 ωm ) and are mounted in interchangeable holders. Designs of the holders and the mounting assembly are presented. The major problem in using stopping detectors at medium energies is the tail of low pulse height events produced by nuclear reactions and scattering out. A technique for rejecting these events is described and the results obtained with deuterons from p-d elastic scattering of 800 MeV protons are presented. Analysis of the nuclear reaction tail for 120, 220, and 250 MeV deutrons yields an average total reaction cross section for deuterons on Ge of σ R = (1490±130) mb.