Kinetic Limitations in Electronic Growth of Ag Films on Fe(100)

Quantum well (QW) resonances are identified in Ag films on an Fe(100) surface and are used in low energy electron microscopy to monitor film morphology during annealing and growth. We find that Ag films thermally decompose to thicknesses that are stabilized by QW states at the $\overline{\Gamma }$ point. Novel growth morphologies are also observed that highlight the competition between kinetic limitations and the QW state energetics that promote electronic growth. These combined observations help to explain the unusual bifurcation mode of thermal decomposition that was reported previously for this system.

Figure 1

Integrated LEEM intensity versus incident electron energy and thickness ($\mathrm{M}\mathrm{L}=\mathrm{\text{monolayer}}$) for Ag films grown on Fe(100) at 300 K. The solid lines through the data are the phase accumulation model predictions for the values of the quantum numbers, $\nu$, that are indicated on the right.

Figure 2

LEEM images of initially uniform (a) 3 layer and (b) 4 layer Ag films on Fe(100) following thermal decomposition at elevated temperature. The imaging energy is 4.5 eV. (c) The local intensity spectra measured in the bright regions in (a) and (b) are compared to the spectrum of the two layer annealed film. (d) The local intensity spectra measured in the dark regions in (a) and (b) are compared to the spectrum of the five layer annealed film.

Figure 3

LEEM images of Ag film growth on Fe(100) at (a)–(d) 420 K and (e)–(h) 455 K. The imaging energy is 5.3 eV. The film thicknesses of different regions are indicated in monolayer units. See Ref. 23.

Figure 4

Schematic drawings of morphologies observed during growth of Ag on Fe(100). The shading in this figure corresponds to the intensity of corresponding features in Fig. 3. The dashed sections indicate double and triple layer growth.