(a) SEM image of AuNx film grown by PLD at 157 nm on Si  substrate in N2 (105 Pa). The AuNx structures have the morphology of elongated self-assembled dendrite micro-islands. (b) Higher magnification of dendrite micro-islands. A micro-size nano sphere is shown too. (c) EDXS of AuNx film. The formation of AuNx is identified by the N peak at 396.6 eV.
(a) SEM image of gold film grown by PLD at 157 nm on Si  substrate in Ar (105 Pa). The plain gold dendrite structures resemblance those of Fig. 1(a). (b) SEM image of plain gold dendrite micro-islands at higher magnification. (c) EDXS of plain gold film.
AFM images and normalized Z height distributions of AuNx and plain gold structures. (a) and (b) Dendrite AuNx structure (film grown in N2). (c) and (d) Granular AuNx nanostructures (film grown in N2). (e) and (f) Plain gold nanostructure (film grown in Ar). (g) and (h) Granular AuNx nanostructures. The Z height distribution of AuNx nanodomains for one scan along the x-axis. The average and maximum height is and , respectively. The surface roughness () and the root mean square surface roughness () are 3.42 nm and 5.178 nm, respectively. The average size of the granular AuNx nanodomains in the plane is ∼54 nm.
Force-distance curve of (a) a 250 μm thick solid gold foil giving a Young's modulus value of 74.6 ± 10 GPa, (b) a 35 nm thick plain gold grain (film grown in Ar) with Young's modulus of 124 ± 10 GPa, (c) a 48 nm thick AuNx nanodomain (film grown in N2) with Young's modulus of 190 ± 10 GPa, a value that is considerable higher than the values of solid (a) and granular gold (b).
Experimental set-up and simplified equivalent circuit. The C-AFM measured output voltage is proportional to the voltage drop along the AuNx nanodomain in the direction of the current flow ( axis) for a scan of the tip along the axis. is the bias voltage of the tip, are the equivalent diodes of the contacts at the points A, B, and is the impedance of the contact.
(a) C-AFM image of a 160 nm AuNx nanodomain. (b) C-AFM signal registered during one scan of the tip along the x axis. The FWHM of the signal at the points A-E reflects the size of the AuNx individual conductive nanodomains (from 6.9 to 16.3 nm), for 7 V bias voltage of the tip.
(a) AFM image of a AuNx granular film structure. (b) C-AFM image of a 200 nm × 200 nm area at the point (4) of (a). (c) C-AFM signal registered during one scan of the tip along the line of (b) in the x axis. The FWHM of the signal at the points A-D reflects the size of the AuNx individual conductive nanodomains (from 10.4 to 15.1 nm), for 7 V bias voltage. Different I-V curves are recorded at the points (1)-(8) and they are indicated in Fig. 9, curves B-H.
Simplified band energy diagram of the MSM contact. are the work functions of the metals, are the build-in potentials at the contacts, are the barrier heights, are the energy position of the edge of the conduction and valance bands and the Fermi levels, is the work function of the AuNx, is separation between the Fermi level and the conduction band of the AuNx, and are the depletion widths of the contacts.
I-V curves of various size AuNx and plain gold nanodomains. The ohmic solid line A is for a plain gold nanodomain. The curves B-H indicate TF emission for different size nanodomains of Fig. 7(a). The size of the nanodomain is obtained from the average value of the size along the axes and is considered to be equal to the contact size of the nanodomain with the gold substrate, Fig. 5.
(a) Logarithm of the current versus the forth root of bias voltage for reverse thermionic emission current, indicating a mismatch between the theoretical and experimental results. (b) Logarithm of the current versus the bias voltage according to the reverse TF emission current, suggesting that TF emission is the dominant charge transport mechanism in AuNx nanodomains.
(a) C-AFM image of a 370 nm long AuNx nanodomain along the x axis. (b) C-AFM signal registered along the line of (a) in the axis for 7 V bias voltage of the tip. The signal at the area near the point A is saturated and cannot be further resolved, while the signal at the point B reveals smaller size nanodomains ().
Logarithmic plot of the “area” versus the size of nanodomain for different bias voltages . The linear fit is in agreement with Eq.(6) confirming TF emission current for AuNx nanodomains.
Normalized height of AuNx nanodomains versus (a) positive bias voltage and (b) negative bias voltage for different values of AuNx work functions. Nanodomains with heights above the values set up by the curves are expected to be conductive.
I-V curve of a AuNx nanodomain, with rectifying response, curve (H) Fig. 9. The retracing path (curve HR), displays pronounced hysteresis compared with the forward path (curve HD), indicating that significant charge memory effects occur in smaller size (z-axis) nanodomains.
EFM images of AuNx nanodomains showing electric stored charges. (a) EFM image of a ∼57 nm AuNx nanodomain with 14 nm maximum height. EFM images of the same sample area recorded with bias voltage −5 V (b) and +5 V (c). (d) Analysis of the EFM phase signal, where contrast inversion occurs in four regions. Comparison of the EFM signals (black line for +5 V bias, blue line −5 V bias) with the AFM topography (red line).
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