| The devices based on Schottky barriers contact exhibit the excellent performance in recent years. The modulating and developing applications in the new fields to Schottky barriers are main research interests. In this paper, we developed several methods to modulate the barrier and the photoresponse, and we discussed the reason for the photocurrent of p-type oxide semiconductor of CuO nanowires. Meanwhile, a method combining the Schottky barriers with lighting was developed for the gas detecting.In the chapter 1, we introduced the background of one dimension optoelectronic nanodevices and the devices based on Schottky barriers. Therefore, we deduce the research objectives and the main research contents in our future works.In the chapter 2, the AC assembly and electrodepositon method were used to deposite Cu on the CuO nanowire of back to back Schottky barrier, the Cu particles deposited changed into CuO through annealing, which made the current increase about two orders. The current transport properties before and after treatment are both dominated by the reverse current of Schottky barriers under image force model. The current increase after treatment results from the formation of another current pathway, which can decrease the barrier height in the CuO nanowire Schottky barriers about 105 meV. The reason for barrier height decreases is the surface states in metal-semiconductor interface are largely reduced by passivating dangling bonds in the annealing process. Then the Cu was deposited on one side of CuO nanowire device assembled, and the device was annealed after that. We obtained a diode with high on-off value. The AC assembly combined with electrodepositon provided a simple and effective method for modulating the surface states and barrier height. On the other hand, we found the nanowires with different diameter on two sides could be made a device with high rectifying value, which provided a new method for building the Schottky diode. Considering the less oxygen absorption on the CuO nanowire, we measured the current transport properties and the curves of photocurrent versus time of CuO nanowire device in air and high pure N2. The mechanism of the photocurrent was discussed; we found that there were two processes for the produce of photocurrent. The photocurrent was intrinsic semiconductor combined with the current produced in the process of photo- absorbed oxygen, respectively. The response and back for CuO nanodevices are really fast.In the chapter 3, considering the current transport properties of ZnO nanowire device could be modulated by surface functionalized with carboxylic compound, we built the single CuO nanowire device first, and then the fluorinated benzenethiol were used to functionalize the surface of CuO nanodevice. After treatment, the current decreased and the contact barrier increased. But it was worth mentioned that the photoresponse increased remarkably. The increase of barrier results from the molecular dipole between the interface of nanowire and electrode after functionalizing, which added a same directional electric field on the built-in field of CuO nanowire, and made the barrier increase finally. At the same time, the added electric field made the separate efficiency of photo-generated electron-hole pairs under lighting. In addition, the ordinal phenol ring aligned on the surface of nanowire was made after functionalizing, which improved the electron transport through hopping among rings through effectiveπ-πstacking of phenol rings. Therefore, the photo-generated electrons could transport the self-assembly molecular layer. At the same time, the photo-generated holes transport in the undepleted core of nanowire, which arrived at the electrode by tunneling, and then the photoresponse increased finally.In the chapter 4, based on the report of the excellent performance of Schottky barriers device on the gas detecting, considering our studies on the Schottky barriers device and the increasing of surface catalyzed activity by lighting, we calculated the effective barrier height of CuO NW device, which decreased with the bias increased. We built the primary experiment equipments of gas sensor, and observed the response of CuO and SnO2 nanodevices to low concentration H2S in dark and lighting under room and high temperature, respectively. We found that the CuO nanodevices had poor response to H2S under room and 200℃without lighting. However, we could detect the change of current at 200℃with lighting. The change of current became saturated with the increase of H2S. A primary model was built to explain the mechanism of response. For the SnO2 Schottky barriers device, the sample had no response to H2S under room temperature, and had the biggest response signal under 250℃, which arrived at 107.4 percent. The response could be increased largely in room and high temperature under UV lighting, which arrived at 797.1 percent in 250℃, especially. Seven times increase was investigated. The main reason for it is still in research. Hopefully, a gas sensor with excellent performance which can work under room temperature and air will be developed.In the chapter 5, we made a conclusion of the researches of this paper, and expected the future investigations on the farther application of Schottky barriers on gas detecting. |
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