Influence of target chemical activity on Balmer lines emission from backscattered hydrogen

We have investigated the influence of implanted hydrogen on Balmer lines em ission from backscattered particles under D+ irradiation to Si target for a n incident energy ranging from 5 to 25 keV at a target temperature from roo m temperature (RT) to 600 K and the experimental results are compared with Monte Carlo simulation by the TRIM92 code. For clean Si surface, D-alpha ph oton intensity was proportional to the backscattering coefficients calculat ed by the TRIM92 code for all incident energies. The intensity stayed const ant with increasing the fluence for incident energies of 15 and 25 keV in a ccordance with the simulation that the backscattering coefficient is not so much influenced by implanted deuterium because the mass of D is much less than that of Si. At 5 keV incidence, the D-alpha photon intensity gradually increased with the fluence until saturated after prolonged irradiation. Th e difference between the initial intensity and that after saturated was red uced with increasing the target temperature and disappeared above 600 K. Th e decay of the D, photon intensity accompanied by the thermal release of im planted deuterium was also observed above 370 K. According to the TRIM92 ca lculation, the D/Si atomic ratio at the top surface for keV incidence with the fluence of 4 x 10(17) D+/cm(2) exceeds 0.4 which is the maximum hydroge n concentration of amorphous hydrogenated Si (a:Si-H), whereas that for 15 keV incidence remains below 0.1 even over the 7 x 10(17) D+/cm(2) irradiati on, All these results made us to conclude that the D-alpha intensity at 5 k eV incidence is enhanced by retained deuterium near the top surface through modifying the electron capture process of backscattered deuteron. (C) 1998 Elsevier Science B.V. All rights reserved.