## 4 Results and Discussion
### Comparison of Electrochemical Properties of MSM Diode  
Indian indigo was reviewed in this work because of its similarities in terms of environment and weather. Its yield extraction was introduced by [PERSON] [28]. The MSM diode was fabricated and its electrochemical properties investigated [18]. A comparison of six electrochemical properties of MSM diodes between the proposed and reviewed ones was investigated and compared with a commercial one, as shown in Table 1[18,28]. The indigo extraction yield of the proposed and reviewed diodes was acquired in the same fermentation conditions of 40 \({}^{\circ}\)C for 24 h. The local indigo shows a yield of concentration twice higher than that of the reviewed indigo because the suitable pH in our fermentation provides a large indican quantity [28]. The I-V characteristics provide the knee voltage, forward- and reverse-bias currents, and calculated static resistance. The knee voltage is a voltage level at which the potential energy of the electron is higher than the band gap energy of the indigo layer, and it also overcomes barrier potential at the MSM junction. It causes the MSM diode to approach the current conduction state at the forward bias. The value of this voltage is dependent on the orbital energy of the indigo layer and the work function of metal electrodes in the device [17]. The 1.0 V\({}_{\text{MSM}}\) of knee voltage is found in our local indigo diode, which is close to that of the commercial diode, 0.7 V\({}_{\text{MSM}}\), whereas that of the review indigo diode is large, at about 2.0 V\({}_{\text{MSM}}\). These results mean that our local indigo diode can easily be improved to operate at 0.7 V\({}_{\text{MSM}}\). The \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multirow{2}{*}{**Commercial Diode**} & \multicolumn{3}{c}{**MSM Diode (Al/Indigo/Cu)**} \\ \cline{3-5}
**Parameter (25 \({}^{\circ}\)C)** & **Diode** & **Review** & **Local Indigo Diode** \\  & [24] & **Indigo Diode** & **1[8,28]** & **1 st Diode** & **2 nd** \\ \hline Indigo yield (mg g\({}^{-1}\)) & - & 0.6 & & 1.03 \\ Knee voltage (V\({}_{\text{MSM}}\)) & 0.7 & 2.0 & 1.0 & 1.01 \\ Highest forward-bias current (mA) & 1000 & 0.014 & 2.60 & 3.19 \\ Average reverse-bias current (mA) & 0.00239 & 0.001 & 0.1 & 0.15 \\ Highest static resistance of & 2090 & 2000 & 97 & 107 \\ reverse-bias (kOhm) & 108 & 8.30 & 32.50 & 19.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Electrochemical properties of local and review indigo of MSM diodes. Figure 6: Rectification ratio of the proposed MSM diodes with local indigo. advantage of the local indigo diode is thought to be due to its greater number of electrons and holes obtained from a high yield concentration during the preparation [29]. It is seen that both forward- and reverse-bias currents of either review or local indigo diodes are much too low to compare with those of a commercial diode. However, a forward-bias current of a local indigo diode is found to be about 2-3 hundred times higher than that of a review one. These results mean that for utilization in a gradual linear amplifier in a positive current, the local indigo diode is more usable than the review one. A nearly zero reverse-bias current is normally required to ensure that a current must flow in only one direction of a positive bias. The reverse-bias current of a review indigo diode is about 100 times smaller than that of our indigo diode. This is possibly because of the difference in an indigo derivative between our local MSM diode and the review one. It may be attributed to that the electron and hole characteristics of both number and mobility in the local indigo are better than those of the review indigo, as it exhibits a lower energy band. Therefore, the local MSM diode is more conductive [22]; this means that both diodes may be used in some particular applications. The static resistance of reverse-bias must have a high value in order to prevent the reverse-bias current from flowing in a negative direction.