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ABSTRACT Deuteron magnetic resonance (DMR) has been used to further examine hydrogen (deuteron) populations in amorphous-silicon (a-Si) and in n-type crystalline silicon (xSi). In both a-Si and x-Si DMR shows central components arising at least in part from isolated molecular deuterium and sharp doublet features from Si-bonded hydrogen (D). Our new results include the observation in x-Si of molecule-specific DMR multiple echoes from trapped ortho-D 2 . A second new result is the observation in x-Si of a substantial Si-bonded D population with splittings between 46 and 80 kHz and perhaps arising from (deuterated) hydrogen H* bond-centered and antibonding configurations.

INTRODUCTION There remain questions concerning the configurations, populations, and dynamics of hydrogen loaded into high quality amorphous and crystalline silicon. In the present work deuteron magnetic resonance (DMR) has been used to compare these systems and particularly to examine T-site-trapped molecular hydrogen and to search for H* configurations.

EXPERIMENT DMR at 30 and 55 MHz has been used between 4.2 and 32 K to examine deuterated amorphous and crystalline Si samples which had been well-characterized by other means. High photovoltaic quality a-Si:D and a-Si:H,D deuterated films were prepared in William Paul's Harvard laboratories by plasma-enhanced chemical vapor deposition from SiD 4 and from SiH 4 +D 2 . Photoresponse products rjpMr and other photovoltaic parameters were measured on intact films [1]. Perdeuterated x-Si:D samples were prepared and characterized [2] at Xerox PARC. After downstream plasma deuteration, crystal sheet slices were reassembled to provide a stacked single crystal bulk sample for DMR. For a P-doped n-type Si sample the deuteration initially was confined to a depth of 200 nm. Prior DMR measurements [3] on high quality a-Si have shown two principal populations: a 66 kHz powder-averaged quadrupolar doublet from bonded Si-D and a 33 kHz FWHM broad central (BC) line from molecular D 2 (and HD) trapped and rather immobile below 180 K. As the temperature increases to 300 K the BC line narrows by a factor of two, which implies the existence of slow motions among molecular trapping sites. Earlier DMR measurements on x-Si have detected [4] a quadrupolar doublet from Si-D bonds lying along (111) directions and a central feature, tentatively ascribed to molecular deuterium (D 2 ). Subsequent DMR studies [5] showed this central feature to have two components, 613 Mat. Res. Soc. Symp. Proc. Vol. 507 © 1998 Materials Research Society

with a fast-relaxing Gaussian feature probably arising from trapped para-D 2 . At longer magnetization recovery times a narrower component also appears. The present experiments have employed a 90,-r- 2 6y DMR pulse sequence to detect deuteron multiple spin echoes specific to trapped ortho-D 2 molecules [6] and the application of 90-r-90y quadrupole echo resonance line shape analyses to characterize other deuteron populations.

RESULTS Molecule-specific ortho-D 2 DMR multiple echoes now have been