Shmuel Bukshpan

Hyperfine interaction study of the decoration of the internal wall of nanosized voids by impurity probes

Abstract We observe the trapping of implanted radioactive 57 Co atoms at empty nano-cavities formed in {111} Si by the desorption of He from bubbles. The absorption of 14.4 keV γ-rays roughly monitors the displacement of the activity, while anodic stripping and counting the remaining 122 keV γ-ray intensity is employed to obtain an accurate depth profile and to isolate the wanted fraction of the sample. Mossbauer spectroscopy shows that only damage and/or CoSi 2 -nuclei related sites are present in samples implanted at 300 and 400°C. In a sample implanted with Co at RT at the same side as the cavity-generating He atoms, the Mossbauer spectra reveal two new quadrupole split components after 30 min annealing at 700°C. We present arguments for the tentative identification of these to a cavity edge site (79%, strong bonding) and to a cavity plane site (21%, weak bonding).

Pressure effects of krypton bubbles on the host aluminium lattice as probed by 57Co impurity atoms

Abstract Metal lattices containing highly pressurized solid rare gas bubbles are strained under pressure. We have studied these internal pressures by performing Mossbauer measurements on implanted 57 Co probe atoms as a function of annealing temperature. We thus identified two sites: a substitutional site and a “new” site. The behaviour of the isomer shift and recoilless fraction of substitutional cobalt indicated a high compression of the aluminium lattice, which reached a pressure of 77 kbar after annealing to 500 K. At 750 K the system started to relax.

A study of amorphous tellurium

Amorphous Te has been prepared by Te ion implantation and by vapour quenching.129mTe was introduced in trace amounts. We confirm previous measurements on the structure of amorphous Te and discuss the bonding. We show that the amorphization by ion implantation is an abrupt phase transformation.

Tetramethyl tin in frozen rare gases. A study of impurity-host binding

Abstract The Mossbauer effect in 119 Sn was applied to obtain information on the local dynamical properties in frozen rare gases. The results show a hardening of th phonon spectrum for the matrix isolated tetramethyl tin molecule in neon and argon. No such enhancement is observed for the matrices of solid krypton and xenon. An explanation based on geometrical considerations is proposed.

Study of the formation of Cs inclusions in refractory bcc metals by133Xe(Cs) Mössbauer resonance

The formation and properties of Cs inclusions in Mo and W are observed through a preimplanted133Xe(Cs) local probe, which is found to reside in three sites: a substitutional site, an interfacial one and a further site which is not detectable directly, but the presence of which can be inferred from the Mössbauer measurements. The location of the probe at the interface of small Cs inclusions is characterized by large Debye temperatures of around 200 K, a quadrupole interaction of +1.86(15) mms−1, which is close to known surface site values, and an isomer shift of −0.33(12) mms−1. From the latter value an approximate local pressure of 5 GPa is deduced. In W the site populations are followed as a function of Cs dose. The observed interchange of populations in the low dose range is thought to represent the initial formation of the second phase inclusions.