To assure proper adhesion of the deposited material to a Ge-wetted substrate Y 27632 surface and to avoid water ice crystal growth, which leads to the increase of substrate roughness, the system should operate at the lowest possible pressures and all the time on the high temperature side of the p-T diagram shown in Figure 3. Optimum deposition temperature Figure 4 shows temperature-dependent plots of surface

morphology parameters: ten-point height, average height, and RMS roughness values measured using AFM on 30-nm-thick Ag films for deposition at temperatures above that of sublimation. Notice the vertical scale different from that in Figure 2. Within the range 230 to 350 K, RMS roughness has nearly ML323 the same value. Two other criteria have minimum values at RT. Figure 4 Three surface morphology parameters measured using AFM on 3 × 3 μm 2 area of 30-nm-thick Ag layers. Thin Ag films were deposited on sapphire substrates with Ge wetting monolayer at temperatures in the range 170 to 400 K. The morphology of crystalline 30-nm-thick Ag layers was analyzed using two-dimensional X-ray diffraction (XRD2). The XRD2 pattern from one of the 30-nm-thick Ag samples deposited at 295 K has a bright spot from the double-sided epi-polished

Al2O3 single-crystal substrate oriented in c-plane (0001) and the weak arc from silver nanocrystallites with periodicity 3.88 Å and random orientation in space (see Additional file 1). Similar XRD2 patterns were obtained also for 10-nm-thick Ag films deposited at temperatures in the range 200 to 350 K. Finally, we consider ATM/ATR mutation the roughness of very thin silver

layers, which are important for construction of hyperbolic metamaterials [26, 27] and plasmonic nanolenses [28–32]. Moreover, nanometer-thick Ag films with low surface roughness and fine crystallinity have low electron oscillation damping loss and thus can guide long-range plasmons [33, 34]. In the 10-nm-thick Ag film, all three morphology parameters are considerably reduced due to the residual influence of the Ag-Ge surface adhesive force. Figure 5a, b shows a 2D AFM image and a 1D profile of the 10-nm Ag film with the lowest value, achieved with physical vapor deposition, ever reported: RMS = 0.22 nm and ten-point height equal Dynein to 1.05 nm. An example of SEM image of the same sample is presented as supporting data in Additional file 2. To illustrate roughness increase with metal film thickness, we show an AFM profile of the 30-nm Ag film in Figure 5c. Figure 5 AFM image and profiles. (a) AFM image of 10-nm-thick Ag film deposited at 295 K. The lowest ever reported morphology parameters for e-beam deposition technique are as follows: ten-point height value = 1.05 nm, average height = 0.9 nm, and RMS height = 0.22 nm. AFM profiles of (b) 10- and (c) 30-nm-thick Ag films deposited at 295 K.