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1.
《Current Applied Physics》2015,15(3):319-325
Pd is one of the metals suitable for inducing low-temperature crystallization in Ge. However, it is not clear how residual Pd atoms are integrated into the Ge lattice. Therefore, time-differential γ–γ perturbed angular correlations (TDPAC) technique using the 100Pd(→100Rh) nuclear probe produced by recoil implantation has been applied to study the hyperfine interactions of this probe in single-crystalline undoped Ge. A Pd-vacancy complex aligned along the <111> crystallographic direction with a unique interaction frequency of 8.4(5) Mrad/s has been identified. This complex was measured to have a maximum relative fraction of about 76(4)% following annealing at 350 °C. Further annealing at higher temperatures reduced this fraction, possibly via dissociation of the complex. Calculations suggest dissociation energy of 1.94(5) eV for the complex. DFT calculations performed in this work are in reasonable good agreement with the experimental values for the electric-field gradient of the defect complex in Ge and Si for comparison. The calculations predict a split-vacancy configuration with the Pd on a bond-centred interstitial site having a nearest-neighbour semi-vacancy on both sides (V-PdBI-V) in Ge and Si.  相似文献   
2.
181Ta time differential perturbed angular correlation (TDPAC) and positron lifetime measurements were carried out on homogeneously α-implanted CuHf samples. TDPAC measurements indicate the trapping of vacancy clusters and helium associated defect complexes by Hf atoms. The presence of helium-vacancy complexes and helium stabilised voids has been identified by positron lifetime measurements. Further the nucleation and growth stages of helium bubbles have been identified. TDPAC and positron lifetime measurements indicate that Hf atoms act as heterogeneous nucleating centers for helium bubbles. Hf atoms are found to suppress the bubble growth in CuHf as indicated by the results of positron lifetime measurements.  相似文献   
3.
Radiation-induced defects are studied in cubic rhodium metal, using the local probe technique ‘Time differential perturbed angular correlation’ (TDPAC) at liquid N2 temperature. Isochronal annealing was done at 300, 1073 and 1473 K temperatures. The irradiated sample showed two quadrupole interaction frequencies at 1150 and 93 MHz. The low frequency disappeared at room-temperature annealing, which was assigned to In trapped at a vacancy, whereas the higher frequency remained up to high temperatures and was attributed to In trapped at Rh–C complexes in the Rh matrix.  相似文献   
4.
Time differential perturbed angular correlation measurements done on the 482 keV level of181Ta probe nuclei in well annealed reference foil samples ofα-ZrHf,α-TiHf andα-Hf indicate that all probe nuclei are defect free, substitutional and experience quadrupole frequencies characteristic of these matrices. But mostly the ratio of the intensities of the harmonic components of the quadrupole frequency is never in 3:2:1, which is understood to be due to the selective orientation of microcrystallites brought out by the pre thermo-mechanical treatments on the sample. This paper illustrates as to how texturing in general could cause ambiguities in the measurements of the hyperfine interaction parameters of probe nuclei particularly in hcp foil samples with or without the association of any defects and the ways to delineate the effect of texturing.  相似文献   
5.
Very unusual energy spectrum and defect production kinetics have been observed under 80Co-y-irradiation and heat-treatment of high-pure germanium. The results can be explained in terms of vacancy-donor and divacancy-donor complexes. The upper limit of the vacancy migration energy in germanium has been estimated as 0.3 eV.  相似文献   
6.
Yaar  I.  MayTal-Beck  S.  Berant  Z. 《Hyperfine Interactions》2001,136(3-8):777-781
The Hf z coordinate and the value of the electric field gradient (efg) main component (V zz ), were calculated for three Hf2X compounds (X = Pd, Ag, Cd) on a first-principle basis, using the full potential linear augmented plane wave (LAPW) method. Exchange and correlation effects were treated either by the local spine density approximation (LSDA) or by the more advanced generalized gradient approximation (GGA). The calculated V zz values, in the Hf site, were in very good agreement with available 181Hf TDPAC experimental results. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   
7.
R G Pillai  S H Devare 《Pramana》1977,8(6):495-499
The quadrupole interaction (QI) of99Ru as a dilute impurity in Zn, Cd and Sn lattices was studied by using time differential perturbed angular correlation technique. The electric field gradients calculated from the measured quadrupole interaction frequencies at room temperature are 5.14 × 1017 volts/cm2 for99RuZn, 4.58 × 1017 volts/cm2 for99RuCd and 2.87 × 1099 volts/cm2 for99RuSn. The temperature dependence of the QI studied in the case99RuZn is similar to that of117InZn.  相似文献   
8.
The g-factor of the first excited state of 93Sr (E = 213 keV, T 1/2 = 4.6 ns) was measured by an on-line TDPAC technique with use of the strong hyperfine field in Fe metal. The Larmor frequency ω L = (2.60 ± 0.15) × 108 rad/s was obtained. The g-factor is derived as g = −0.227 ± 0.013 from g = −ℏω L/B hf μ N. If the spin of the first excited state of 93Sr is assumed to be 3/2, the g-factor is predicted by a simple core-excitation model as g = −0.22, which is in good agreement with the present experimental result.  相似文献   
9.
Time Dependent Perturbed Angular Correlations of -rays (PAC) can be used to study hyperfine interactions of a dynamic nature. However, the exact effect of the dynamic interaction on the PAC-spectrum is sometimes difficult to derive analytically. A new approach based on Monte Carlo simulations is therefore suggested, here implemented as a Fortran 90 program for simulating PAC spectra of dynamic electric field gradients of any origin. The program is designed for the most common experimental condition where the intermediate level has spin 5/2, but the approach can equally well be used for other spin states. Codes for 4 different situations have been developed: (1) Rotational diffusion by jumps; used as a test case. (2) Jumps between two states with different electric field gradients, different lifetimes and different orientations of the electric field gradient principal axes. (3) Relaxation of one state to another. (4) Molecules adhering to a surface with random rotational jumps around the axis perpendicular to the surface. To illustrate how this approach can be used to improve data-interpretation, previously published data on 111mCd-plastocyanin and 111Ag-plastocyanin are re-considered. The strength of this novel approach is its simplicity and generality so that other dynamic processes can easily be included by only adding new program units describing the random process behind the dynamics. The program is hereby made publicly available.  相似文献   
10.
Pal  G.  Sebastian  K. C.  Somayajulu  D. R. S. 《Hyperfine Interactions》2001,136(3-8):613-617
TDPAC study of InBi1−x Te x with x=0.0, 0.01, 0.05, 0.1 and 0.2 as a function of temperature is done. Both pure and Te-doped samples show a semi-metallic character up to around room temperature. Above room temperature a steep transition to semiconducting state was observed, which is independent of the doping concentrations. Hence Te may be in the interstitial sites. Conductivity measurement of the above samples showed the same trend as observed in the EFG studies. Thus the importance of the conduction electron density is prominently seen in these systems. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   
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