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AFM images for two pieces from the same wafer (a) AFM image for as grown sample and (b) AFM image for 26 times etched sample.
(a) Temperature dependence of the field cooled moment of layer A measured after every 5th stage of the thinning process. (b) Reduction of the saturation moment [taken as K)] versus number of the thinning step. Dashed line defines the thinning efficiency . Calculated layer thickness of the remaining material, , is given on the right y-axis.
(a/top) Experimentally determined values (full points) and results of modeling of Curie temperature in 15 nm (Ga,Mn)As as a function of decreasing layer thickness d (dashed and solid lines). (a/bottom) Hole profiles for various values of d calculated by solving the Poisson equation with the negative gradient of the concentration of Mn at interstitial sites and electrostatic effects present at the top and bottom boundaries of the layer. (b1)-(b3) Squares— and bullets— projection of the thermoremnant moment at elevated temperatures recorded for: (b1) as grown layer, (b2) after 5th step, and (b3) after 10th step of thinning. The corresponding layer thickness is quoted. The vertical dashed line marks an arbitrary selected temperature T = 94 K at which thickness-driven spin reorientation transition is observed. Arrows indicate for these cases.
Literature data on (given in units of the effective Mn concentration, ) of (Ga,Mn)As plotted as a function of thickness d. Open symbols—as grown, bullets—after annealing, and diamonds—present data. Where not explicitly stated, the values have been calculated according to Ref. 7. Essentially, the same picture is obtained if alone is plotted.24 The thick dashed line is a guide indicating the main trend of improvement of on the lowering of d.
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