Weak localization effects in ZnO surface wells

Hall effect, magnetoresistance, and electrical conductivity measurements, c arried out on ZnO surface wells created by a large variety of methods, are analyzed in the frame of the weak-localization theory. The ZnO surface well s have some unique features that allow the investigation of the weak-locali zation effects: ZnO has a single valley conduction band; the Thouless lengt h is much larger than the elastic mean-free path even at room temperature; the well accumulates the largest surface electron concentration obtained up to now in a surface quantum well; there are a large variety of preparation methods, some of them making it possible to modify independently both the width and the depth of the surface wells. These features allowed us to inve stigate: the presence of the weak-localization effect in the largest range of temperatures(1.6-300 K) reported up to now for a quantum well; the influ ence on the transport properties of the increase in the number of subbands in the well; the effect of the presence of more inelastic scattering mechan isms and their weights in the entire scattering process; and the passage fr om a quasi-two-dimensional system to a three-dimensional one. [S0163-1829(9 9)01932-3].