AES and EELS study of alkali-metal adsorption kinetics on either cleaved or sputtered GaAs and InP (110) surfaces

A detailed study at room temperature of the interfaces between thin alkali films and cleaved or sputtered processed (110) surfaces of GaAs and InP has been performed using Auger and electron energy loss spectroscopy. Attention has been focused on the interface growth kinetics, and on subsurface intermixing and segregation processes in the presence of different metals (Cs, Na and K) and substrates. The most relevant features in the interface formation are very similar in all cases. Alkali adatoms partially diffuse in the semiconductor subsurface. For K and Na on GaAs, this intermixing also results in an As outdiffusion. On sputter-prepared substrates, the interface formation rate is lower, the As outdiffusion on the contrary is larger and occurs also in the Cs/GaAs case. A comparison with high and low electronegativity metals on III–V semiconductors is made and the results are discussed. As far as interfacial reaction and products are concerned, we found that cations and anions are predominantly involved in the chemical bonding with the adatoms in GaAs and in InP, respectively.