This application claims priority of Taiwanese Patent Application No. 104100385, filed on Jan. 7, 2015.
The disclosure relates to a method of a manufacturing a photoelectric and thermoelectric sensor, and a photoelectric and thermoelectric sensor.
A conventional thermoelectric device includes at least one thermoelectric unit including a P-type semiconductor element and a N-type semiconductor element connected to the P-type semiconductor element. When a temperature difference is present between the P-type and N-type semiconductor elements, current flow is generated in the conventional thermoelectric device.
Manufacture of the conventional thermoelectric device is complicated, time-consuming and costly.
Therefore, an object of the disclosure is to provide a method of manufacturing a photoelectric and thermoelectric sensor, and a photoelectric and thermoelectric sensor made therefrom, that can alleviate at least one of the drawbacks associated with the conventional thermoelectric device.
According to a first aspect of the present disclosure, a method of manufacturing a photoelectric and thermoelectric sensor includes the steps of:
According to a second aspect of the present disclosure, a photoelectric and thermoelectric sensor includes a porous silicon substrate and an electrode unit. The electrode unit is disposed on and connected to the porous silicon substrate, and is adapted for being connected to an external circuit.
Other features and advantages of the present disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which:
Before the present disclosure is described in greater detail with reference to the accompanying embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the disclosure.
Referring to
In order to decrease contact resistance, the electrode unit 23 may be made of gold. The porous silicon substrate 22 may be a p-type silicon substrate. In this embodiment, the porous silicon substrate 22 is a p-type silicon substrate with a thickness of 525±25 μm. A distance between each of the first protruding portions 235 of the first electrode 231 and an adjacent one of the second protruding portions 236 of the second electrode 232 is not greater than 0.6 mm.
Referring to
To be more specific, an electrochemical etching apparatus 3 (see
The silicon substrate 21 is fixed between the anode 35 and the O-ring 33. The O-ring 33 hermetically seals a gap between the silicon substrate 21 and the reaction vessel 32. The etching solution 31 is added into the reaction vessel 32 and the cathode 34 is then dipped into the etching solution 31. The silicon substrate 21 is electrochemically etched under the conditions that the current density of the power supply 36 is 50 mA/cm and the temperature of the etching solution 31 is ranged from 20° C. to 40° C. Note that the current density may be altered according to practical requirements. The electrochemical etching is performed for 20 minutes to 40 minutes. For example, the electrochemical etching may be performed for 20 minutes to 30 minutes. During the electrochemical etching process, a reduction reaction producing hydrogen ions take places at the cathode 34 so as to release hydrogen gas, and an oxidation reaction takes place at the anode 35 such that the silicon substrate 21 contacting the anode 35 is etched to form the porous silicon substrate 22, with pore sizes ranging from 10 nm to 100 nm.
It should be noted that shapes of the pores of the porous silicon substrate 22 may change with the concentration and composition ratio of the etching solution 31. Sizes of the pores are likely to be increased with an increase of the current density of the power supply 36. Therefore, desired pore sizes can be obtained by using desired etching solutions and adjusting the current density. Isopropyl alcohol is used to reduce etching rate and increase etching uniformity to obtain the porous silicon substrate 22 having finer and more evenly distributed pores. A weight ratio of hydrofluoric acid to isopropyl alcohol to deionized water in the etching solution 31 is 1:2:1 or 1:3:1.
Preferably, before etching, the silicon substrate 21 is ultrasonically washed with deionized water, acetone and ethanol in sequence and is then blow-dried with nitrogen.
The electrode unit 23 formed on the porous silicon substrate 22 may be the one shown in
To form the interdigitated electrode unit 23 on the porous silicon substrate 22, thermal evaporation deposition with the use of a shadow mask is used. To be more specific, the shadow mask with a pattern corresponding to the pattern of the interdigitated electrode unit 23 is laminated on the porous silicon substrate 22. Gold is evaporated under vacuum, and is deposited on the porous silicon substrate 22 so as to form the interdigitated electrode unit 23 on the porous silicon substrate 22. The thickness of the interdigitated electrode unit 23 may be 50 nm and can be changed according to practical requirements.
The following examples and comparative examples are provided to illustrate the embodiments of the disclosure, and should not be construed as limiting the scope of the disclosure.
A photoelectric and thermoelectric sensor 2 having the structure shown in
A photoelectric and thermoelectric sensor 2 having the structure shown in
The photoelectric and thermoelectric sensor 2 of Example 3 was similar in structure to that of Example 2, except that the distance between each of the first protruding portions 235 and an adjacent one of the second protruding portions 236 was 0.6 mm.
The method for forming the photoelectric and thermoelectric sensor 2 of Example 4 was similar to that of Example 2, except that the weight ratio of hydrofluoric acid to isopropyl alcohol to deionized water in the etching solution 31 was 1:2:1. The structure of the photoelectric and thermoelectric sensor thus obtained was similar to that of Example 2, except that the distance between each of the first protruding portions 235 and an adjacent one of the second protruding portions 236 was 0.6 mm.
The method for forming the photoelectric and thermoelectric sensor of Comparative Example was similar to that of Example 4, except that the etching solution was composed of hydrofluoric acid (HF) and ethanol (EtOH) at a weight ratio of 1:1.
The thermoelectric property of the photoelectric and thermoelectric sensor 2 of Example 2 was determined.
Specifically, referring to
During the heating process, temperature differences between the first and second main portions 233, 234, and corresponding current flows were recorded as shown in Table 1.
As shown in Table 1, the photoelectric and thermoelectric sensor 2 of E2 is capable of producing current flow in response to the temperature difference between the first and second electrodes 231, 232. The current flow increased with an increase of the temperature difference.
Similar to the procedure in Determination Of Thermoelectric Property, in each of the photoelectric and thermoelectric sensor of E1 to E4 and CE, a first region I and a second region II were defined. The first and second electrodes 231, 232 respectively in the first and second regions I, II of the photoelectric and thermoelectric sensor of E1 were connected to an ammeter 25. Similarly, the first and second main portions 233, 234 in each of the photoelectric and thermoelectric sensors of E2 to E4 and CE were connected to an ammeter 25. In each of the photoelectric and thermoelectric sensors, the first region I was first illuminated by a light source (e.g. an LED, a laser, etc.). The second region II was then illuminated by the light source. Current flows generated by the photoelectric and thermoelectric sensor were measured by the ammeter 25 and were recorded.
Tables 2 and 3 show the maximum current flow for each of the photoelectric and thermoelectric sensors.
According to Table 2, each of the photoelectric and thermoelectric sensors 2 of E1 to E4 is capable of transforming light energy into electric energy. Based on the results of the Examples 2 and 3, the current flow increases with an increase in the distance between each of the first protruding portions 235 and an adjacent one of the second protruding portions 236.
As shown in Table 3, compared with the sensor of the Comparative Example, the photoelectric and thermoelectric sensors 2 manufactured by the method of this disclosure (i.e., the Examples 1, 3 and 4) generate higher current flows and have better photoelectric property.
To sum up, by virtue of the etching solution used in the electrochemically etching step, the photoelectric and thermoelectric sensors 2 exhibiting superior photoelectric and thermoelectric properties can be obtained. The conventional structure composed of N-type and P-type semiconductor elements can be omitted. The manufacturing process can be simplified and the cost thereof can be reduced.
While the disclosure has been described in connection with what are considered the embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Number | Date | Country | Kind |
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104100385 | Jan 2015 | TW | national |