## 2 Materials and Methods
### Tip Integration to MEMS  
This work aims to investigate the possibility of using PtC tips in quantum tunneling vacuum gap applications. Therefore, the results and findings of the HRTEM analysis will be validated in a MEMS consisting of a PolySi beam and an electrostatic actuator. After deposition and patterning of the nano-tip to the beam, the tunneling effect can be proved by measuring the tunneling current between two PtC electrodes at distances of some nm. For a deeper insight into this subject, the authors published their work in another survey [15]. The process of tip integration to the MEMS is shown in Figure 3.  
Figure 3a shows the initial state of the PolySi beam with a thin gold (Au) layer for a high conductivity of the structure. The fabrication of the MEMS is carried out by the foundry service PolyMUMPs from MEMSCAP Inc. and subsequent micro structuring of the tunneling electrodes with a focused ion beam. PolyMUMPs is a surface micro-machining process with three polysilicon layers, two sacrificial layers, and a metal layer. The minimum structure size for PolyMUMPs is 2 \(\upmu\)m. The standardized process procedure with strict adherence to the design rules ensures low manufacturing times and costs. Since the application of this tunneling device proves a vacuum gap tunneling mechanism by varying the tip distance, the PolySi beam must be divided into movable and fixed parts. Therefore, the PolySi beam is patterned by the FIB in the first process step illustrated by Figure 3b. As shown in the preparation of the tips for the HRTEM analysis, it is necessary to fabricate the nano-tips in several steps. After deposition of a PtC pad by the FIB or the FEB and the GIS (Figure 3c), the pad is milled subsequently by the ion beam to obtain a thin vertical nanobeam (Figure 3d) and a final cut with a small ion current of 1.5 pA to provide two opposing tunneling tips (Figure 3e). The smallest size of the initial PtC pad depends on the technology and chosen beam current. The FEBID allows a much finer deposited structure than the FIBID. Moreover, the same can be seen on different ion currents. As lower the ion current is chosen, as higher the resolution of the deposited pad. The initial pad in Figure 3c is based on the FIBID with a 260 pA current. Due to attractive forces between the tips [15], the tips' radii are patterned by the FIB as sharply as possible. To measure and verify the tunneling current between the PtC tips, the MEMS is connected to a two-channel Source Measuring Unit (SMU) Tektronix Keithley 2614b, as shown in Figure 4a. The MEMS-Chip is bonded by a Wire Bonder G5 Single (F&K Delvotec) to a printed circuit board (PCB) (Figure 4b). One channel operates the electrostatic actuator to approach the tip of the movable part towards the fixed tip below. The second channel is loaded by the tunneling bias voltage in the range of 100 mV to 1 V and measures the  
Figure 3: Process of tip integration to the MEMS with (**a**) the initial state of the PolySi beam, (**b**) the basic patterning of the beam to obtain a fixed and a movable part, (**c**) the deposition of a PtC pad, (**d**) patterning of the PtC pad and (**e**) the final PtC nano-tips/electrodes by dividing the nanobeam by the FIB. occurring tunneling current at final tip distances of a few nm. Figure 4c shows the PolySi beam structure with the actuator in top view, and Figure 4d depicts the final PtC tip in side view. Although this application enables the measurement of external forces to the MEMS (in the case of an accelerometer or pressure sensor), in this study, the static approach of the tips is only provided to prove the ability of quantum tunneling between organic-metal materials and their dependence on the FIB/FEB fabrication parameters. The approach of the tips is performed by several small voltage steps (1-5 mV) using the electrostatic actuator. The measuring point for every voltage step on channel 1 and the tunneling current on channel 2 is saved by the SMU to a log file.