Growth of ultrathin rare-earth films studied byin situx-ray diffraction

Abstract

We present in-situ x-ray scattering measurements performed during the growth of two rare-earth metals, gadolinium and samarium, onto molybdenum (110) single crystals. The results have been interpreted using a diffusive growth model to determine the degree of interlayer mass transport in the initial stages of deposition. Both elements are shown to grow generally in a layerwise manner but with significant roughness after the initial layer is complete. A raised substrate temperature modifies the growth; the best Gd single layer is produced at a temperature of 140°C when deposited at a rate of 0.067 monolayers/min while for Sm the growth becomes increasingly islanded at higher temperatures. The presence of oxygen at the surface encourages layer-by-layer growth for both Gd and Sm, although a significant proportion of the atoms are in upper layers before the lower ones are complete. The mechanism for improved layerwise growth is oxide formation at the interface, producing a large amount of small islands that encourage interlayer mass transport. The growth of Sm on Mo (110) is generally more rough than Gd on Mo(110) due to the dynamic size change associated with the coordination induced valence transition for the Sm atoms.

Growth, morphology, and structure of a monolayer thickGdFe2surface alloy

“…2 upper curve) shows an initial peak due to monolayer completion followed by a shoulder at 2 ML. These results are consistent with those of Nicklin et al [9] who also report that subsequent growth tends to be disordered. As the proportion of Fe increases, the initial peak diminishes and the second peak becomes more apparent.…”

“…3(a) with percentages of Gd and Fe within the monolayer of 78 ± 2.5% and 27 ± 2.5%, respectively. This gives a total occupancy of 105 ± 2.5% for the first ML and indicates that the initial layer contains 5% extra atoms than expected, in agreement with similar findings by Nicklin et al [9] for a pure Gd film.…”

“…The adsorption of Gd on the Mo(110) and (112) surfaces has been previously studied by Nicklin et al [9,10] and Waldfried et al [11], respectively. Growth on the corrugated (112) surface results in a strained Gd overlayer that shows preferential domain growth along the [111] direction.…”

Energy-dispersive X-ray reflectivity and GID for real-time growth studies of pentacene thin films

“…While X-ray growth oscillations at one point in reciprocal space have been routinely monitored in growth studies [11,12,[14][15][16], the energydispersive technique offers the advantage of simultaneously measuring a wide q-range, i.e. a large number of Fourier components are sampled.…”

Dependence of STM Images οn Bias Polarity for Sm Layers οn Mo(110) and Mo(211) Surfaces

“…The issue of Sm valence has been studied in a great number of papers devoted to investigations of the Sm thin films deposited on various metallic [18][19][20][21][22][23][24][25] and semiconductor substrates [26][27][28][29]. However, STM investigations of Sm surfaces are scarce, and we are aware of only a few papers concerning STM investigations for Sm layers on Si(111) and Si(100) [27,28], on Mo(110) [20], and on low-index Cu surfaces [24,25].…”