G. S. Sandhu

Reactive ion etching of diamond

A reliable means of removing surface layers of diamond is of significant importance for microelectronics as well as for other applications such as polishing of the diamond surface. Preliminary studies using reactive ion etching with O2 and H2 showed etching rates of the order of 560 A/min for thin carbon films and 350 A/min for natural type II‐A diamonds using 300 eV oxygen ions. Addition of a substantial percentage of Ar to oxygen in the reaction chamber did not affect the etching rate.

Doping of diamond by coimplantation of carbon and boron

We have implanted boron ions into insulating natural diamonds which were predamaged by carbon ion implantation in order to enhance the doping efficiency. All implantations were performed at liquid‐nitrogen temperature. Subsequent rapid thermal annealing at 1100 °C produced strong new optical absorption bands near 1060 cm−1, and a sharp absorption at 2962 cm−1 (0.37 eV) which is close to that attributed to substitutional boron in type IIB diamond. We obtained resistivity of the order of 100 Ω cm and carrier activation energy of 0.1 eV for a sample implanted with 2×1015 C and 3×1014 B per cm2, indicating a high substitutional fraction of boron atoms.

Regrowth of radiation-damaged layers in natural diamond

Abstract The regrowth of radiation-damaged layers created by carbon ion implantation in natural diamond was investigated by the Rutherford backscattering/channeling technique and by optical absorption. We present the first results of rapid thermal annealing of the implanted samples directly from the 77 K implantation temperature to 1100° C as well as data for isochronal annealing. We found that isochronal annealing up to 900° C was more effective than rapid thermal annealing for amorphized samples. The critical dose for amorphization of diamond was between 1.65 × 1015 and 3 × 1015 cm−2 for 200 keV carbon ion implantation at 77 K.

Transient diffusion of boron implanted in SI along random and channeling directions

Abstract We have studied anomalous diffusion of boron implanted into silicon along the [100] channeling direction versus random directions for 5, 10, and 40 keV, 2 × 1014 cm2 boron implantations. Three different annealing conditions, 800 °C for l h, 900 °C for 30 min, and 1000 °C for 10 s, were studied. Anomalous diffusion was observed for all implants annealed at all conditions. The amount of enhanced diffusion is 10–50% higher in the implants along the channeling direction than along the random directions. We attribute the mechanism of the diffusion enhancement to the annealing of ion implantation damage. The difference of diffusion enhancement between channeled implants and random implants are due to the difference in damage profile of the two different implants. Electrical activity of boron is observed for random and for channeled implantations, and the shape of the Hall profile agrees with that of SIMS.

Ion channeling analysis of MBE grown Si1−xGex/Si strained layer superlattices

Abstract Strained layer superlattices (SLSs) of Si1−xGex/Si, consisting of four pairs of layers, each about 40 nm thick with x = 0.16-0.25, have been grown on Si(100) by molecular beam epitaxy (MBE). The SLSs were characterized by Rutherford backscattering (RBS)/channeling, double crystal diffractometry (DCD), and cross-sectional transmission electron microscopy (XTEM) techniques. Tetragonal distortion in the Si1−xGex layers, caused by the lattice mismatch between Si and Si1−xGex, was measured by RBS/channeling and DCD. The strain measured by these two techniques agreed well with that calculated from the theory of elasticity and Monte Carlo simulation. XTEM investigation of the SLSs showed a dislocation-free structure and smooth interfaces.

A Study Of The Doping Process In Diamond By Boron Implantation

Type IIa diamond crystals were implanted with boron ions with or without prior carbon ion implantation. The samples were kept at liquid nitrogen temperature during both implantation steps. A strong near-edge optical absorption band appeared after implantation, and partially recovered during annealing at 800 °C. For the highest B implantation fluence, optical absorption peaks at 2800 to 3000 cm-1 were observed that were in the same vicinity as the absorption peaks attributed to substitutional boron atoms in natural p-type diamond. Electrical measurements for three of the samples demonstrated well-defined activation energies that could be associated with hopping conduction and/or activation of B dopant atoms. This work shows that p-type doping in diamond by boron ion implantation is feasible, using a suitable combination of low temperature implantation and subsequent annealing.