## 3 Results
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Parameters** & **1** & **2** & **3** & **4** & **5** & **6** & **7** \\ \hline SiH\({}_{4}\) (sccm) & 9.8 & 9.8 & 9.8 & 9.6 & 9.6 & 9.6 & 9.6 \\ N\({}_{2}\) (sccm) & 6 & 6 & 6 & 6 & 6 & 6 & 6 \\ ICP (W) & 200 & 200 & 200 & 200 & 200 & 200 & 200 \\ RF (W) & 0 & 10 & 0 & 0 & 0 & 5 & 0 \\ APC (mTorr) & 7.9 & 7.9 & 7.6 & 6 & 8 & 8 & 8.2 \\ DR (nm/min) & 17.88 & 18.80 & 17.64 & 16.66 & 17.50 & 18.90 & 18.70 \\ \(n\pm 0.013\) & 2.398 & 2.498 & 2.378 & 2.443 & 2.385 & 2.449 & 2.293 \\ \(k\pm 0.006\) & 0.011 & 0.008 & 0.030 & 0.006 & 0.032 & 0.020 & 0.018 \\ Stress (MPa) & \(-138\) & \(-152\) & \(-172\) & \(-150\) & \(-135\) & \(-157\) & \(-118\) \\ Roughness (nm) & 0.41 & 4.5 & 0.91 & 0.26 & 0.23 & 4.4 & 0.53 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Deposition parameters of silicon-rich SiN\({}_{\text{x}}\) and their results in refractive index, coefficient, stress gradient and roughness for recipes 1–7. Negative stress denotes compressive. Table 2 summarises the 9 different architectures for our MEMS ordered from smaller to larger electrode area (\(A\)), the cavity length (\(L_{cav}\)) in nm and Young's modulus \(E\) in GPa. The cavity length, i.e., the distance between the MEMS mirror and the bottom Bragg mirror depends on the MEMS architecture with two main empiric findings: (i) for low areas of the arms \(A=WL\), the elastic modulus scales approximately linearly with arm area as more material is compressively stressed. The elastic modulus saturates around 90 GPa for an area around 1000 \(\upmu\)m\({}^{2}\). There is only one exception, namely, \(W=33\ m,\ L=28\) m; however, the elastic modulus of the next smaller case is within the error bar of the simulation. (ii) The cavity length scales about quadratically with the product of elastic modulus and width, \(L_{cav}=a\cdot(E\cdot W)^{2}+h_{0}\) as Figure 4 shows. This feature can be used as design rule for cavities. Figure 5 shows the tunability in transmission for a FP-cavity with 23 \(\upmu\)m long and 33 \(\upmu\)m wide arms, corresponding to a cavity length of 651 nm (c.f. Table 2). At zero bias, the main transmission resonance is centred at 1542.9 nm, i.e., in the middle of the C band. Upon thermal tuning, the main transmission peak shifts out of the range covered by the tunable diode laser, yet reaching a peak wavelength of 1629.6 nm at a tuning current applied to the top electrode of 60 mA while keeping a constant base temperature of 16 \({}^{\circ}\)C. The full width half maximum is 0.70 \(\pm\) 0.1 nm, averaging overall the main peaks shown in the figure. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \(W\) & \(L\) & \(A\) & \(L_{cav}\) & \(E\) \\ \(\pm\)**0.25 (\(\upmu\)m)** & \(\pm\)**0.25 (\(\upmu\)m)** & (\(\upmu\)m\({}^{2}\)) & \(\pm\)**30 (nm)** & \(\pm\)**12(GPa)** \\ \hline
33 & 18 & 594 & 614 & 56 \\
33 & 23 & 759 & 651 & 63 \\
48 & 18 & 864 & 1485 & 80 \\
33 & 28 & 924 & 733 & 70 \\
48 & 23 & 1104 & 1635 & 88 \\
63 & 18 & 1134 & 2685 & 89 \\
48 & 28 & 1344 & 1725 & 90 \\
63 & 23 & 1449 & 2770 & 90 \\
63 & 28 & 1764 & 2850 & 92 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of architecture parameters of MEMS, cavity length in every case and estimated elastic modulus. Figure 3: Reflectivity band of 6.5-layer pair silicon-rich SiN\({}_{x}\)/SiO\({}_{y}\) on a Si substrate. Measured by ellipsometry at 40\({}^{\circ}\), simulation at 40\({}^{\circ}\), \(\sigma\)- and \(\pi\)-polarisation, and simulation at vertical incidence.