AVS 45th International Symposium
    Surface Science Division Monday Sessions
       Session SS-MoP

Paper SS-MoP25
Adsorption and Reaction of H@sub 2@O on GaAs(100)

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Surface Science Division Poster Session
Presenter: X.M. Wei, National University of Singapore
Authors: X.M. Wei, National University of Singapore
Q.P. Liu, National University of Singapore
Y.T. Wong, National University of Singapore
H.H. Huang, National University of Singapore
G.Q. Xu, National University of Singapore
Correspondent: Click to Email
The adsorption and reaction of H@sub 2@O on Ga-rich GaAs(100) surface have been investigated using TDS and HREELS. During the H@sub 2@O dosage at 100 K, we believe the adsorption proceeds as follows: initially, molecular H@sub 2@O is adsorbed, probably onto Ga. For a higher exposure at about 0.28 L, a 2-D H@sub 2@O monolayer is built. A subsequent dose increase leads to phase transition from a 2-D monolayer to a 3-D H@sub 2@O multilayer. During heating to 500 K, the desorption follows the reverse scheme. The H@sub 2@O multilayer is first desorbed at about 170 K, as detected by TDS, which makes the surface resemble that prepared by exposure at 0.28 L. On heating to a higher temperature, the remaining H@sub 2@O molecules are desorbed by 250 K. On the other hand, the first monolayer H@sub 2@O dissociates to give hydroxyls and hydrides. Hydroxyls are bound to Ga sites while hydrides tend to occupy As sites. More hydrides are formed from the further dissociation of Ga-bound hydroxyl. These hydrides adsorb onto Ga sites which are left vacant after the recombinative desorption of Ga-bound hydroxyl. At ~500 K, H@sub 2@ gas is also liberated.