Calorimetric studies of crystallization and relaxation of amorphous Si and Ge prepared by ion implantation

Abstract

Amorphous Si and Ge layers, produced by noble gas (Ar or Xe) implantation of single crystal substrates, have been crystallized in a differential scanning calorimeter (DSC). The MeV implantation energies resulted in amorphous layers of micron thickness whose areal densities were determined using the Rutherford backscattering and channeling of 1-MeV protons. These techniques allow determination of the amorphous-crystal interface velocity (which is proportional to the rate of heat evolution ΔḢac) and the total enthalpy of crystallization ΔHac. Amorphous Ge was found to relax continuously to an amorphous state of lower free energy, with a total enthalpy of relaxation of 6.0 kJ/mol before the onset of rapid crystallization. The interface velocity for crystallization on (100) substrates, was found to have an Arrhenius form with an activation energy of 2.17 eV. The value of ΔHac was found to be 11.6±0.7 kJ/mol, the same as for samples prepared by deposition. For Si, ΔHac was determined to be 11.9±0.7 kJ/mol without any evidence of heat release due to relaxation. The (100) interface velocity was found to have an activation energy of 2.24 eV. The effects of the implant depth profile on the regrowth velocity could also be observed directly in the DSC signal. From the value of ΔHac and Gibbs free-energy calculations, the melting temperature of amorphous Si has been determined to be Taℓ =1420 K.

Quantification of the bond-angle dispersion by Raman spectroscopy and the strain energy of amorphous silicon

“…Integration of ⌬c ac ͑Si͒ from 0 to 1000 K gives 1.5 kJ/mol, which is similar to the result we would obtain with the estimation for ⌬c ac ͑Si͒ used by other authors 47 …”

Effect of Non-Hydrostatic Stress on Kinetics and Interfacial Roughness During Solid Phase Epitaxial Growth in Si

“…al. [11], Eq. (4) can be well fit using all three forms for DF(∆G) to Olson and Roth's SPEG rate data [4] (measured over ten decades in growth rate) by simply adjusting v 0 and ∆E*.…”

Role of activation energy in resistance drift of amorphous phase change materials

“…In a last step, the phase change material and a suitable capping material, (ZnS) 80 :(SiO 2 ) 20 , was sputter deposited in-situ within the same sputtering tool. The capping material serves as a barrier for potential oxidation and outgassing of the phase change material during annealing.…”

“…Thus, it is prone to structural relaxation as is the case for all amorphous materials. In amorphous silicon, amorphous carbon and metallic glasses structural relaxation has been characterized by numerous techniques [18][19][20][21][22][23]. It is therefore not clear a priori whether the resistance drift observed in phase change materials is a material specific phenomenon or rather a general consequence of the materials being glasses.…”