AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA1
Atomic-Scale Analysis of the SiH@sub 3@ Surface Reactivity During Plasma Deposition of Amorphous Silicon Thin Films

Wednesday, November 17, 2004, 2:00 pm, Room 210C

Session: Surface Collision Dynamics
Presenter: M.S. Valipa, University of California, Santa Barbara
Authors: M.S. Valipa, University of California, Santa Barbara
E.S. Aydil, University of California, Santa Barbara
D. Maroudas, University of Massachusetts, Amherst
Correspondent: Click to Email
Hydrogenated amorphous silicon (a-Si:H) thin films grown by plasma-assisted deposition are used widely in the fabrication of solar cells and flat panel displays. The dominant precursor for deposition of device-quality a-Si:H films is the SiH@sub 3@ radical. Development of systematic strategies for depositing a-Si:H films with desirable properties requires a fundamental understanding of surface reactions of the SiH@sub 3@ radical leading to a-Si:H growth and H incorporation. This presentation focuses on detailed atomic-scale analysis of the surface reactions of SiH@sub 3@ using molecular-dynamics simulations of repeated impingement of SiH@sub 3@ radicals on growth surfaces of smooth a-Si:H films. The corresponding surface reaction probability, @beta@, is determined over the temperature (T) range 475-800 K. SiH@sub 3@ can either incorporate into the film by adsorbing onto a dangling bond or inserting into Si-Si bonds (sticking), or abstract surface H through Eley-Rideal (ER) or Langmuir-Hinshelwood (LH) pathways to produce SiH@sub 4@ gas, or react with another surface SiH@sub 3@ to desorb as Si@sub 2@H@sub 6@ (recombination), or leave the film by reflection or desorption. The overall @beta@ (sticking + recombination) is almost constant over the T range studied, as are the probabilities for sticking and recombination, s and @gamma@, respectively. Energetic analysis shows that SiH@sub 3@ adsorption and insertion and ER abstraction are barrierless processes, which explains the measured T independence of @beta@. LH abstraction is activated at high T, but competes with Si@sub 2@H@sub 6@ formation, yielding a T-independent @gamma@. Also, LH abstraction leads to H elimination from a-Si:H during growth and explains the T dependence of H content in the a-Si:H film.