Hydrogen desorption from crystalline silicon and its modification due to the presence of dislocations

Abstract

Hydrogen effusion spectra of oxidized Si samples are investigated and characteristic activation energies associated with the rupture of hydrogen bonds are estimated. Dislocation-enhanced solubility of hydrogen is found in deformed crystals and macroscopic diffusion depth (mm) can be realized. Hydrogenation is performed by exposure of the crystals to H2 gas at 800 °C. Beside the desorption of hydrogen bound close to the Si surface, the rupture of hydrogen-hydrogen bonds of molecules stored in deformed crystals is observed. The storage of the H2 molecules requires the presence of dislocations or deformation-induced point defects, and the H:H binding energy ranges from 2.7 to 3.8 eV. Most likely this energy variation comes from different local strain around dislocations. Atomic hydrogen is found to dominate the effusion kinetics.