Experimental studies of long-range atomic H motion and desorption in hydrogenated amorphous silicon and germanium

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5574727

Wu, Xiaolin

Long-range H motion and desorption in low hydrogen concentration undoped hydrogenation amorphous silicon (a-Si:H) and germanium (a-Ge:H) was studied by deuterium secondary ion mass spectrometry (SIMS) depth profiles and IR absorption of a-Si:H/a-Si:(H,D)/a-Si:H and a-Ge:H/a-Ge(H,D)/a-Ge:H. SIMS monitors deuterium motion (assumed similar to that of H), while IR yields information on hydrogen content and bonding. The diffusion constant was found to be dispersive with time, and depended on H content C{sub H}, diffusion length L, and microvoid content, at temperatures T {le} 400C for a Si:H and T {le} 310C for a-Ge:H. It exhibited a power-law D(t) = D{sub oo}({omega}t){sup {minus}{alpha}} relation in both systems. In a-Si:H, {alpha} generally deviates from the 1 {minus} T/T{sub o} dependence on the temperature T expected from a multiple trapping mechanism. The diffusion constant at constant diffusion length D(t{sub L}) then deviates from an Arrhenius dependence on the temperature. The apparent activation energy E{sub a} and prefactor D{sub o}, defined by the linear best-fit of InD(t{sub L}) vs 1/T, strongly increase with L at low C{sub H}. The Meyer-Neldel relation (MNR) D{sub o} = {bar A}{sub oo} exp(E{sub a}/T{sub o}{prime}), where {bar A}{sub oo} {approx equal} 3.1 {times} 10{sup 14}cm{sup 2}/s and T{sub o}{prime} {approx equal} 730 K, holds for all 1.3 {le} E{sub a} {le} 2.4 eV and 2.5 {times} 10{sup {minus}5} {le} D{sub o} {le} 3,100 cm{sup 2}/s. The diffusion results for both a-Si:H and a-Ge:H are discussed in relation to the microstructure of the films. The nature of the microvoid-induced deep H-trapping sites is also discussed. Finally, a possible relation between the dispersive diffusion and a percolation model is presented.

• Research Organization: Iowa State Univ. of Science and Technology, Ames, IA (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5574727
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
AMORPHOUS STATE
ATOMS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DATA
DESORPTION
DIFFUSION
ELEMENTS
EXPERIMENTAL DATA
GERMANIUM
HYDROGEN
HYDROGENATION
INFORMATION
ION SPECTROSCOPY
METALS
MICROSTRUCTURE
NONMETALS
NUMERICAL DATA
PERMEABILITY
SEMIMETALS
SILICON
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRAPPING