AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA7
Observation of Adsorption and Reaction of NH@sub 3@ on Al@sub 2@O@sub 3@, AlN and AlON Under Steady-State Conditions Using IRRAS

Thursday, November 5, 1998, 4:00 pm, Room 316

Session: Non-destructive Testing and In-situ Diagnostics
Presenter: V.M. Bermudez, Naval Research Laboratory
Correspondent: Click to Email
The surface chemistry of Al@sub 2@O@sub 3@, AlN and Al oxynitride ("AlON") with NH@sub 3@ is important in the MOCVD growth of GaN on these substrates. Thin films of Al@sub 2@O@sub 3@, AlN and AlON have been grown by reacting a NiAl(111) surface with O@sub 2@, NH@sub 3@ or NO, respectively.@footnote 1@ The resulting buried-metal-layer structures have then been employed as substrates for studies of NH@sub 3@ adsorption under steady-state conditions, at 300 K and up to 200 Torr, using polarization-modulated fourier-transform infrared reflection absorption spectroscopy. For Al@sub 2@O@sub 3@ evidence is seen, in the form of a change in the LO phonon, for incorporation of N into the surface to form a dilute "AlON-like" phase. The @delta@@sub s@ symmetric deformation mode of adsorbed NH@sub 3@ is easily detected under high (@>=@25 Torr) static pressures. For AlN, no evidence of adsorbed NH@sub 3@ is seen in a 200 Torr ambient. For AlON, distinct surface and volume LO phonon modes are seen, with the former responding reversibly to chemisorbed NH@sub 3@. The @delta@@sub s@ frequency indicates a lesser degree of Lewis acidity on AlON vs. Al@sub 2@O@sub 3@ surfaces, which may favor 2D GaN growth on AlON by increasing the surface mobility of NH@sub x@ species. For each of the three materials, IRRAS also provides useful information about the structural quality of the films prior to NH@sub 3@ exposure. @FootnoteText@ @footnote 1@Franchy et al., Appl. Phys. A 65 (1997) 551.