Carbon nitride films synthesized by nitrogen ion beam bombarding on C60 films

\valunit*{400}{\eV} or ) nitrogen ion beam was used to bombard films to synthesize carbon nitride films. The bombarded films were examined by Raman and X-ray photoelectron spectroscopy (XPS) measurements. The experimental results showed that the destroyed carbon species chemically combined with nitrogen ions to form stable carbon nitride. An appropriate beam energy (possibly ) was proposed in this method. Received: 1 July 1996/Accepted: 27 November 1996     

Formation of NaCl-type Cr carbide by carbon ion implantation

A new NaCl-type simple structured fcc chromium carbide was observed after 50 keV carbon-ion implantation into pure Cr thin films. The lattice constant was 0.403 nm determined by electron diffraction. TEM in situ annealing showed that the new phase was stable up to a temperature around 300°C. Auger spectra confirmed the formation of the carbide. The formation energy of the carbide calculated by Miedema's empirical method was –7 cal/mol.     

Supersaturated Si-As alloy formation by ion implantation and pulsed electron beam annealing

Supersaturated surface alloys produced by very high dose (0.8–2.6×10¹⁷cm^–2) implantation of As-ions into silicon and subsequent pulsed electron-beam annealing have been investigated by means of the channeling technique. The maximum solubility limit of 7×10²¹ As/cm³ has been determined. It exceeds the equilibrium solubility limit by more than a factor of 4. Angular scan measurements indicated that for doses above 1×10¹⁷cm^–2 As atoms are displaced by about 0.12 Å from the regular lattice sites.     

Impurity and concentration dependence of growth rate during solid epitaxy of implanted Si

The increase of the growth rate during solid-phase epitaxy in silicon implanted with B, P, As, and Sb is explained in terms of strain in the host lattice due to the addition of the dopant. The growth rate increases proportionally to the strain thus taking into account both species and concentration dependence below the solid solubility limit. The strain itself is in a simple way related to the difference between the tetrahedral covalent radii of Si and of the dopant.     

CW CO2-laser annealing of arsenic implanted silicon

CW CO₂-laser annealing of arsenic implanted silicon was investigated in comparison with thermal annealing. Ion channeling, ellipsometry, and Hall effect measurements were performed to characterize the annealed layers and a correlation among the different methods was made. The laser annealing was done with power densities of 100 to 640 W cm⁻² for 1 to 20 s. It was found that the lattice disorder produced during implantation can be completely annealed out by laser annealing with a power density of 500 W cm⁻² and the arsenic atoms are brought on lattice sites up to 96±2%. The maximum sheet carrier concentration of 6×10¹⁵ cm⁻² was obtained for 1×10¹⁶ cm⁻² implantation after laser annealing, which was up to 33% higher than that after thermal annealing at 600 to 900°C for 30 min.     

Saturation and isotope mixing during low-temperature implantations of hydrogen into metals

Deuterons of 10 keV energy and protons with the same mean projected range have been implanted into several metals at a temperature of approximately 35 K and at dose rates of approximately 2 × 10¹⁴ cm^–2 s^–1. The amount of retained deuterium saturates at fluences larger than roughly 2 × 10¹⁸ cm^–2. After implantation of deuterons and subsequent bombardment with protons, the deuteron depth profiles show characteristic double peak structures, which indicate a replacement process. The experimental data are in good agreement with a simple model of local saturation and mixing. The possible implications of this model are discussed.     

Passivation of laser induced defects in silicon by low energy hydrogen ion implantation

It is well established that the pulsed-laser annealing of as-implanted Si introduces electrically active defects. The aim of this paper is to show that these defects can be neutralized by low-energy hydrogen ion implantation. The techniques used for the sample characterization are current-voltage measurements and capacitance transient spectroscopy.     

Influence of ion implantation on the thermal diffusivity of semiconductors

The influence of ion implantation on the thermal diffusivities of semiconductors are studied using the mirage effect. The dependences of the thermal diffusivities on the implantation doses are obtained. For silicon wafers implanted by boron, phosphorus and arsenic ions, with constant implantation energy, the thermal diffusivities decrease with increasing dose, when the doses are less than some critical values. The theoretical calculation results by using a one-dimensional multilayer model are in good agreement with the experimental ones. On the other hand, for gallium-arsenide wafers implanted with silicon ions, it is found experimentally that the thermal diffusivity increases with the implantation dose.     

Nd: YAG laser annealing of gallium-implanted silicon

A Q-switched Nd: YAG laser with a pulse duration of 20 ns was used to investigate effects of laser annealing in gallium implanted silicon. Rutherford backscattering and Hall-effect measurements were performed to evaluate the annealed layer. Differential Hall-effect measurements were carried out to obtain carrier concentration profiles after annealing. It was found that a maximum sheet carrier concentration of 8×10¹⁵ cm⁻² can be obtained for a gallium implantation of 10¹⁶ cm⁻² by laser annealing with an energy density of more than 1.0 J cm⁻². Although the peak carrier concentration was found to be 8.0×10²⁰ cm⁻³, the annealed layer showed polycrystalline structures even after annealing with an energy density up to 4J cm⁻². The annealing took place in the solid phase in this energy density range.     

Front and back surface cw CO2-laser annealing of arsenic ion-implanted silicon

The annealing behavior of arsenic-implanted silicon under scanned cw CO₂-laser irradiation from front and back surfaces is investigated. Ellipsometry, Hall effect, Rutherford backscattering measurements and neutron activation analysis indicate an enhancement of annealing efficiency by laser irradiation from the back surface, which provides complete recovery of crystal damage, high substitutionality and electrical activation of implanted arsenic atoms without redistribution of concentration profile. The enhancement of annealing efficiency under back-surface irradiation is explained by the difference in laser reflection from the front and back surface of silicon wafers. No differences in the results are found for scanned and static annealing.     

Investigation of laser-annealed antimony implanted Si by ion backscattering and channeling and structure analysis

Rutherford backscattering (RBS), ion channeling and surface studies were done to investigate diffusion of ion implanted Sb in Si. Clean and polished Si was implanted by 190KeV Sb⁺ ions to a dose of 2.3×10¹⁵cm^–2. Laser annealing was carried out by a single 10 J/cm² laser pulse from a Nd: glass (7 ns FWHM) laser. Concentration profiles of Sb as a function of depth and dopant substitutionalities were measured by helium-ion backscattering and channeling. The laser shot resulted in melting of the central portion of the spot. A honey comb type surface morphology was found by SEM analysis. Dektak surface profiles showed a crater of 600 nm depth. One-dimensional heating calculations show that dopant diffusion depths, after consideration of simultaneous evaporation, can be 400 nm, whereas experiments indicate larger depths (1 m). Calculated crater depth is roughly twice the experimental value. Measured depths are much larger than calculated by heat diffusion and indicate that regrowth and distribution of Sb has been modified by convection in the melt. We estimate good substitutionality up to 4 J/cm² and discuss energy density dependence for such high-energy density laser pulses.     

Damage anneal of antimony/phosphorus double implants in silicon

A method is presented for avoiding the dislocation generation in (100) silicon implanted with phosphorus doses up to 5×10¹⁵ ions/cm² at 50 keV. The residual defects after the damage anneal are considerably reduced if the phosphorus implant is combined with a low dose, e.g. 1×10¹⁴ ions/cm², antimony implant which produces a deeper surface layer of amorphous silicon. It is essential that the phosphorus ions are implanted shallower than the antimony ions, and come to rest within the amorphous layer. Subsequent thermal annealing proceeds by a solid phase epitaxial regrowth mechanism.     

Near-surface defects in hydrogen-plasma-treated boron-doped silicon studied by positron beam spectroscopy

Near-surface vacancy-type defects have been studied by positron beam spectroscopy in three boron-doped Si wafers; a control sample, second sample exposed to atomic hydrogen in electron cyclotron resonance (ECR) plasma, and a third sample annealed at 500 °C following plasma treatment. From the analysis of the Doppler broadening spectra, measured as a function of positron implantation depth, we obtain positron diffusion lengths of about 100 and 250 nm for the damaged layer and bulk of the wafer, respectively. For the plasma-treated wafer, our measurements provide a defect density of about 5×10¹⁷ cm^-3. Received: 4 September 1998 / Accepted: 5 January 1999 / Published online: 28 April 1999     

High concentration effects of ion implanted boron in silicon

The diffusion behaviour of implanted boron in silicon was investigated using the¹⁰B(n,α)⁷ Li nuclear reaction. An anomalous behavior with a strong reduction of the diffusivity above an effective solubility limit at 1.5×10¹⁹, 6×10¹⁹, and 1.1×10²⁰ cm⁻³ was found for annealing temperatures of 800, 900, and 1,000°C, respectively.     

Approximation to the two-step diffusion profile by a series of gaussian functions

The two-step diffusion profile is approximated by a series of gaussian functions. Its accuracy is dependent upon the number of terms used in the series, but independent of the number and the spacing of exact data points.     

Enhancement of minority carrier lifetime in GaAs1? x P x ( x =0.4; 0.65) by nitrogen implantation

Minority carrier lifetimes in nitrogen implanted GaAs_1-x P _x (x=0.4; 0.65) were measured at 77K by an optical phase shift method as a function of nitrogen dose and annealing temperature in order to investigate the dependence of the lifetime on the concentration of nitrogen isoelectronic traps. A large increase in the lifetime was observed after nitrogen implantation followed by annealing at and above 800°C. The maximum lifetimes were 22ns for GaAs_0.35P_0.65 and 6.7 ns for GaAs_0.6P_0.4. They were obtained by implantation to a dose of 5×10¹³ cm⁻² in GaAs_0.35P_0.65 and 10¹³ cm⁻² in GaAs_0.6P_0.4. The lifetime after nitrogen implantation followed by annealing was longer by a factor of 6–7 than that of the unimplanted sample.     

Oxidation state of Fe and Ti ions implanted in yttria-stabilized zirconia studied by XPS

The oxidation state of Fe and Ti ions implanted in yttria stabilized zirconia (YSZ) was studied by XPS (X-ray photoelectron spectroscopy) in combination with depth profiling using Ar⁺ sputtering. In the as-implanted state of the sample Fe was found to be present as Fe³⁺, Fe²⁺ and as metallic Fe⁰. This is in agreement with earlier conversion electron Mössbauer Spectroscopy measurements. For Ti-implanted YSZ in the as-implanted state the majority of the Ti is present as Ti⁴⁺, Ti³⁺, and Ti²⁺ ions, while a part of the Zr cations is present in the divalent oxidation state (Zr²⁺). After oxidation in air, the Fe and Ti ions are present only in the valence three and four oxidation states, respectively.     

A model of strain relaxation in hetero-epitaxial films on compliant substrates

0 these maximum relieved strains are φ₀/2, φ₀, 3φ₀/2 and 2φ₀ respectively, at the end of each of stages I–IV. Films relaxed in each stage are characterized by a specific set of macroscopic crystallographic features that can be observed experimentally, including lattice rotation, lattice tilt, and the presence of more than one variant in some cases. For example, complete untwisting is predicted for stage IV relaxation, resulting in the disappearance of the initial twist angle between the two lattices. To relax the elastic misfit strain, extensive plastic deformation of the substrate film is involved, thus making it compliant to the hetero-epitaxial film. This thin film substrate may be called the plastically compliant substrate (PCS). Received: 18 June 1997/Accepted: 27 June 1997     

Photoelectrochemical etching of ZnS: Further evidence for non-uniform flow of charge carriers in Schottky barriers

It is shown that short photoelectrochemical etching of two kinds of ZnS crystals leads to a reduction in the surface recombination velocity as evidenced by their increased photocurrent. The unique surface morphology (>10⁹ pits cm^–2) revealed after photoetching supports the hypothesis that the charge flow within the space charge layer is highly nonuniform.Incumbent of Helen & Milton A. Kimmelman Career Development Chair in perpetuity established by Helen and Milton A. Kimmelman, New York, NY     

Thermal redistribution of boron implants in bulk silicon and SOS type structures

The redistribution of boron profiles in bulk silicon and SOS (silicon-on-sapphire) type structures is investigated in this paper. Experimental data on thermally redistributed profiles are correlated with predictions based on a computer program whose numerical algorithm was described in an earlier paper. Three cases were considered which involved the thermal redistribution of 1) a high dose (2×10¹⁵ and 5×10¹⁴ cm^–2) 80keV boron implant in (111) bulk silicon, in an oxidizing ambient of steam at 1000°, 1100°, and 1200°C, respectively; 2) a high dose (2.3×10¹⁵ cm^–2) 25 keV boron implant in (100) silicon-on-sapphire, in a nonoxidizing ambient of nitrogen at 1000 °C; and 3) a low dose (3.2×10¹² cm^–2) 150 keV boron implant in (100) bulk silicon, in oxidizing and nonoxidizing ambients that make up the fabrication schedule of an-channel enhancement mode device. For all three cases the overall correlation of computer predictions with experimental data was excellent. Correlations with experimental data based on SUPREM predictions are also included.