Gas-assisted silver deposition with a focused electron beam

Focused electron beam induced deposition (FEBID) is a flexible direct-write method to obtain defined structures with a high lateral resolution. In order to use this technique in application fields such as plasmonics, suitable precursors which allow the deposition of desired materials have to be identified. Well known for its plasmonic properties, silver represents an interesting candidate for FEBID. For this purpose the carboxylate complex silver(I) pentafluoropropionate (AgO2CC2F5) was used for the first time in FEBID and resulted in deposits with high silver content of up to 76 atom %. As verified by TEM investigations, the deposited material is composed of pure silver crystallites in a carbon matrix. It showed good electrical properties and a strong Raman signal enhancement. Interestingly, silver crystal growth presents a strong dependency on electron dose and precursor refreshment.

S2 Supp1: Area determination for the calculation of the resistivity ρ of the deposited line Figure S1: AFM height profile of the deposited line. The cross sectional area was determined by integration within the borders (red markers).

Figure S2:
The voltage that was measured in dependency of the current applied gave a linear graph. Referring to Ohm's law (R = U/I), the graph's slope corresponds to R.
The resistivity ρ of the deposited material was determined by solving Equation S1:

S3
with R the resistance measured during four point probe resistance measurements, A the cross sectional area of the line deposit and l the probed distance between the sensing electrodes. Figure S1 is an exemplary AFM height profile of the line deposit used for determining A.
The profiles are taken from the part in between the sensing electrodes. A was determined by integration of the total area for 12 profiles and resulted in average to be A = 0.29 ± 0.03 µm 2 . l was measured in the scanning electron micrograph Figure 4a and determined to be 1.57 µm. By applying a current to the electrodes, the resulting voltage was measured between the sensing electrodes. Due to the linear behavior, Ohm's law applies and was used to determine the resistance R (see Figure S2). The average resistance of 15 measurements at room temperature resulted in R = 197.73 ± 18 Ω. Thus the resistivity ρ could be calculated according to Equation S1.
Supp2: Beam profile of the electron beam used for deposition  To determine the beam profile of the system's electron beam at the corresponding acceleration voltage of 25 kV and beam current of 0.25 nA, a lacey carbon TEM grid was used because of its sharp contrast at the edges of the holes (see Figure S3). The high magnification images were analyzed in ImageJ and the corresponding (smoothened) profile of grey values at the edge was derived, giving a Gauss shaped beam profile as shown in Figure S4. The full width at half maximum could be determined to be FWHM = 400 nm and the full width containing 99.9% of the electrons is determined to be FW(99.9%) = 1.05 µm. Table S1 lists the FWHM for all beam parameters used in this work which were determined in the same way as explained above.  Gaussian of given FWHM and amplitude (see Figure S4). The first parameter was determined using scanning electron micrographs of lacey carbon TEM membranes (see some electrons counted in BSE distribution were generated by the same mechanism as secondary electrons, the secondary electron yield was not applied in order to preserve compatibility between simulations and experiments during renormalization.

Supp4: Autocatalytic growth behavior
In order to determine if AgO2CC2F5 exhibits autocatalytic growth, four square deposits were deposited with an electron dose of each 0.06 nC/µm 2 at a substrate temperature of 160 °C but varying time of gas supply without further electron irradiation, referred to as autocatalytic growth time t(AG). The t(AG) was varied between 0 and 60 min. The deposits were characterized with HR-SEM and EDX. The results are summarized in Figure S5. The silver content variation is <1 atom %. The precursor does not exhibit autocatalytic growth upon gas exposure without further electron irradiation.