Carina Zaring

Multivariate analysis method for energy calibration and improved mass assignment in recoil spectrometry

Abstract Heavy ion recoil spectrometry is rapidly becoming a well established analysis method, but the associated data analysis processing is still not well developed. The pronounced nonlinear response of silicon detectors for heavy ions leads to serious limitation and complication in mass gating, which is the principal factor in obtaining energy spectra with minimal cross talk between elements. To overcome the above limitation, a simple empirical formula with an associated multiple regression method is proposed for the absolute energy calibration of the time of flight-energy dispersive detector telescope used in recoil spectrometry. A radical improvement in mass assignment was realized, which allows a more accurate and improved depth profiling with the important feature of making the data processing much easier.

Low-Temperature Annealing of Radiation-Induced Degradation in 4H-SiC Bipolar Junction Transistors

Radiation hardness is tested for 4H-SiC n-p-n bipolar junction transistors designed for 1200-V breakdown voltage by implanting MeV protons and carbon ions at different doses and energies. The current gain is found to be a very sensitive parameter, and a fluence as low as 1 × 10⁷ cm^-2 of 10 MeV ¹²C can be clearly detected in the forward-output characteristics, I_C(V_CE) . At this low dose, no influence of ion radiation is seen in the open-collector characteristics, I_B(V_EB), or the reverse bias leakage and breakdown properties. Moreover, by annealing the implanted devices at 420°C for 30 min, a complete recovery of the electrical characteristics is accomplished.

Solid solubility and diffusion of boron in single‐crystalline cobalt disilicide

The temperature dependence of the solid solubility [CsCoSi2(B)] and the lattice diffusion coefficient [DCoSi2(B)] of boron in single‐crystalline cobalt disilicide (CoSi2) has been investigated between 450 and 1000 °C. Both CsMCoSi2(B) and DCoSi2(B) are found to be considerably higher than the corresponding quantities in silicon. Using a thermodynamical interpretation, the experimental data show that boron‐doped CoSi2 can be described as a regular solution in the dilute limit with an enthalpy of solution of ∼−0.4 eV. The experimental data and theoretical estimates of the excess enthalpy of solution indicate a weak interaction of boron with the silicon and cobalt atoms in CoSi2 suggesting that the boron atoms occupy sites in the CoSi2 lattice with a small contribution to the Gibbs energy of the solution phase. The diffusion data yield a high mobility of the boron atoms with an activation energy of ∼2.0 eV for the lattice diffusion coefficient which is ∼1.0 eV lower than that reported for the self‐diffusion ...

RBS and recoil spectrometry analysis of CoSi2 formation on GaAs

Abstract Mass and energy-dispersive recoil spectrometry has recently reached the state of development where it is possible to separately characterise Ga and As in GaAs samples. Since it is possible to simultaneously characterise several elements (light as well as heavy), e.g. C, O, Si, Co, Ga and As, the technique is suited for examining the depth distribution of metallisation contacts on GaAs. In a Swedish-Australian collaboration a recoil detector telescope was attached to a beamline of the FN tandem accelerator “ANTARES”, at Lucas Heights Research Laboratories, Australia. In the measurements presented here, 127 I 10+ at an energy of 77 MeV was employed to analyse GaAs samples with thin film overlayers — Si(220 nm)/Co(50 nm)/〈100〉-GaAs. A reference sample and samples annealed at 300 to 600°C were analysed. The measurements showed that CoSi 2 is formed during annealing at and above 500°C with no detectable reaction between the GaAs-substrate and the CoSi 2 overlayer.

Boron redistribution during formation of nickel silicides

Abstract Redistribution of boron during the formation of the nickel silicides Ni2Si, NiSi and NiSi2 has been studied using secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). Both nickel and boron seem to diffuse fast along the grain boundaries in the growing silicide, without any mutual interference. The boron atoms in the consumed silicon redistribute during silicide formation without changing the dopant concentration level in the underlying non-consumed silicon substrate. The boron atoms accumulate at the silicide surface and form a distribution in the silicide at the silicide/ silicon interface that resembles a nearly exponential shape.

Recoil spectrometry : ion accelerator based elemental characterisation of surface layers

Recoil Spectrometry covers a group of techniques that are very similar to the well known Rutherford backscattering Spectrometry technique, but with the important difference that one measures the recoiling target atom rather than the projectile ion. This makes it possible to determine both the identity of the recoil and its depth of origin from its energy and velocity, using a suitable detector system. The incident ion is typically high-energy (30–100MeV)35C1,81Br or127I. Low concentrations of light elements such as C, O and N can be profiled in a heavy matrix such as Fe or GaAs. Here we present an overview of mass and energy dispersive recoil Spectrometry and illustrate its successful use in some typical applications.

Isotope separation and growth mechanisms of intermetallic phases: An investigation of nickel silicides by secondary ion mass spectrometry

Isotope separation resulting from the diffusion‐controlled growth of reacted films has been proposed as a tool to elucidate the diffusion mechanism which controls the growth. A ‘‘reverse’’ isotope separation would be indicative of a grain boundary diffusion mechanism. Such an isotope separation has been studied by secondary ion mass spectrometry (SIMS) during the growth of nickel silicides (Ni2Si and NiSi) for different experimental growth conditions: silicon substrate orientation, temperature of reaction, and silicide thickness. In every case, the isotope separation resulting from the diffusion‐controlled growth is below the accuracy of the SIMS measurements. This is consistent with the fact that isotope effects are usually very small. The difficulties of such studies and the multiple SIMS artifacts encountered at interfaces—matrix effects, variations in the sputtering yield, mass interferences, and sequential acquisition of data—are analyzed in detail. They are found to be quite important in the case of...

Empirical characterisation of mass distribution broadening in ToF-E recoil spectrometry

Abstract The mass broadening function in mass and energy dispersive recoil spectrometry using a detector telescope for time-of-flight and energy determination, has been characterised for a number of isotopes in the range A = 12 to 197. The broadening was well described by a Gaussian function where the standard deviation is given by the empirical equation: θ A ( E, A ) = C 1 + C 2 A 3/2 E − 1 + C 3 A 2 E − 2/3 + C 4 AE 1/2

Lattice diffusion of boron in bulk cobalt disilicide

The lattice diffusion of boron implanted in cobalt disilicide (CoSi2) has beenstudied. The bulk COSi2 substrate, prepared by solidification from a melt, has grain sizes in the millimetre range, thus minimizing the interference from grain boundary diffusion. Boron was introduced into the COSi2 substrate by ion implantation, and after heat treatments ranging from 450 °C to 700 °C the boron distribution was monitored by secondary ion mass spectrometry. The diffusion coefficient was determined from the shape of the resulting boron profile by means of a numerical fitting procedure where the actual shape of the as implanted profile was taken into account. An activation energy of 2.1 eV was found for the lattice diffusion of boron in COSi2, and the lattice diffusion coefficient can be represented in an Arrhenius form as: Dlattice e = 0.9 exp (−2.1/kT)* cm2 s−1.

Recoil spectrometry of thin film reactions in the Pd/InP system

Interfacial reactions between (100) InP and Pd were investigated as part of a systematic study aimed at investigating the stability of planar nonalloyed metallizations to InP. A 50‐nm‐thick Pd film was deposited on an InP substrate, and parts of it were subsequently thermally treated for 30 min at temperatures varying from 100 to 500 °C in steps of 50 °C. Separate characterizations of the Pd, In, and P depth distributions were obtained using mass and energy dispersive recoil spectrometry. The different phases were determined using x‐ray diffraction, and scanning electron microscopy was used to study the surface topography. It is assumed that the interaction starts in the as‐deposited sample, and definite formation of a ternary phase with the suggested composition Pd5In2P2 starts at an annealing temperature of 100 °C. At 250 °C all Pd is chemically reacted. Preferential outdiffusion of P leads to a loss of P from the surface at 500 °C, and the only phase observed in the x‐ray diffraction spectrum from the ...