CN114497271A - NiO/SiO with vertical structure2/ZnO ultraviolet detector and preparation method thereof - Google Patents

Abstract

NiO/SiO with vertical structure₂A/ZnO ultraviolet detector and a preparation method thereof relate to an ultraviolet detector, in particular to a detector added with SiO₂And the p-NiO/n-ZnO ultraviolet photoelectric detector of the insulating layer. The ultraviolet detectors are respectively arranged from bottom to topIs quartz substrate, ITO electrode layer, NiO film, SiO₂Thin film, ZnO thin film and Al electrode layer. The method comprises the early stage of polycrystal p-NiO and SiO₂And preparing an n-ZnO film and performing post-annealing treatment. The device of the invention has good sensitivity to ultraviolet light, good rectification characteristic, low dark current and excellent device performance.

Description

NiO/SiO with vertical structure2/ZnO ultraviolet detector and preparation method thereof

Technical Field

The invention relates to an ultraviolet detector, in particular to a detector added with SiO₂And the p-NiO/n-ZnO ultraviolet photoelectric detector of the insulating layer.

Background

The ultraviolet detection technology is a new technology based on the atmospheric transmission and attenuation characteristics of ultraviolet (10-400nm) radiation and a high-performance ultraviolet optical sensor. Ultraviolet detection technology has emerged in the 50 s of the last century and has begun to enter into substantial research and applications until the 80 s of the last century. Ultraviolet photoelectric detectors have wide and important applications in ultraviolet communication, biochemical analysis, open fire detection, ozone detection and the like, and thus have attracted great research interest at home and abroad. In recent years, wide band gap metal oxide semiconductor materials, such as ZnO, NiO, TiO, have been studied in many ultraviolet detecting materials₂、SnO₂、Ga₂O₃And the like, which are hot materials for research in the field because they exhibit excellent photoelectric properties in the field of ultraviolet detection. The wide band gap metal oxide semiconductor material is characterized by difficult oxidation, small size, sensitive reaction, easy operation and the like. Among them, as representative of the third generation semiconductor materials, in the early 90 s of the last century, Tang et al realized the microcrystalline optical pumping ultraviolet laser emission of ZnO at room temperature, and raised the hot tide of research on the photoelectric properties of ZnO semiconductor materials internationally. The performance of ZnO-based ultraviolet detectors is continuously optimized, and has become one of the hot spots in research in the field of ultraviolet detection.

With the continuous progress of research, in order to optimize the device performance of the oxide-based ultraviolet photodetector, it is proposed to combine two oxide semiconductor materials into a heterojunction device. The preparation of p-type ZnO is difficult and unstable, and industrialization cannot be realized, so that the preparation of p-ZnO and n-ZnO heterojunction devices becomes a difficult problem. Therefore, the search for a p-type material which can be matched with the lattice of the ZnO material and is stable becomes an urgent problem to be solved for optimizing the performance of the heterojunction device. NiO (Eg-3.6eV) is a rare and stable intrinsic p-type material, is simple to grow, has high photoelectric response characteristic only in an ultraviolet light wave band, and becomes a preferred material for forming a heterojunction by combining with n-type ZnO. And the lattice mismatch degree of the NiO and ZnO materials is small, so that the NiO and ZnO materials have great application potential in the field of ultraviolet detection.

Disclosure of Invention

The invention provides a method for preparing a silicon dioxide film by simply adding SiO₂A method for improving the performance of NiO/ZnO heterojunction ultraviolet photoelectric detector by an insulating layer and a device thereof are provided.

NiO/SiO with vertical structure₂the/ZnO ultraviolet detector is characterized in that the functional layer of the detector is NiO/SiO₂/ZnO, adding SiO between p-ZnO and n-ZnO heterojunction₂An insulating layer.

NiO/SiO with vertical structure₂the/ZnO ultraviolet detector comprises a quartz substrate, an ITO electrode layer, a NiO film and SiO from bottom to top respectively₂Thin film, ZnO thin film and Al electrode layer.

NiO/SiO with vertical structure₂The preparation method of the/ZnO ultraviolet detector comprises the following steps:

step 1, substrate cleaning: carrying out wet cleaning on the quartz substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water according to the volume ratio of 1:1: 3;

step 2, sputtering NiO/SiO₂ZnO film: sequentially carrying out radio frequency magnetron sputtering on NiO and SiO on an ITO substrate₂And a ZnO film; the vacuum degree of the equipment is pumped to 7.0 multiplied by 10^-4Pa below;

setting the sputtering pressure at 0.6-0.8Pa, the sputtering power at 180-;

setting the sputtering pressure at 0.8-1.0Pa, the sputtering power at 80-120W and the sputtering time at 35-55min to obtain SiO₂A thin film having a thickness of about 5 to 22 nm;

setting the sputtering pressure at 0.7-0.9Pa, the sputtering power at 180-220W and the sputtering time at 60-80min to obtain the n-ZnO film with the thickness of 80-120 nm.

Step 3, annealing: the prepared film is annealed in a tube furnace at 500-600 ℃ for 25-35min at the heating rate of 8-10 ℃/min.

Step 4, evaporating an Al electrode: and (4) evaporating and plating an Al electrode on the surface of the n-ZnO.

The SiO₂And the thickness of the film is about 20 nm.

The invention adoptsPreparing p-NiO/SiO on ITO coated quartz substrate by radio frequency magnetron sputtering method₂The ultraviolet photoelectric detector has a/n-ZnO simple vertical structure. By adding SiO of suitable thickness₂The device structure is regulated and controlled by means of the insulating layer, and the performance of the device is further optimized. Under the condition of not adding substrate temperature, polycrystal p-NiO and n-ZnO films are prepared, and the crystallinity of the films is better. The preparation process is simple, the cost is low, the device has good sensitivity to ultraviolet light, good rectification characteristic and low dark current, and the device has excellent performance.

Drawings

FIG. 1 shows the p-NiO/SiO₂The structure of the/n-ZnO heterojunction device is shown schematically.

FIG. 2 shows the p-NiO/SiO₂I-V analysis result chart of/n-ZnO heterojunction device.

FIG. 3 is a diagram of I-V analysis results of the prepared p-NiO/n-ZnO heterojunction device.

FIG. 4 shows the p-NiO/SiO₂The responsivity (R) of the/n-ZnO heterojunction device is shown as a graph along with the change of bias voltage.

FIG. 5 shows the p-NiO/SiO₂The detectivity (D) of the/n-ZnO heterojunction device is plotted as a function of bias voltage.

FIG. 6 shows the p-NiO/SiO₂I-V analysis result chart of (7nm)/n-ZnO heterojunction device.

FIG. 7 shows the p-NiO/SiO₂I-V analysis result chart of (10nm)/n-ZnO heterojunction device.

FIG. 8 shows the p-NiO/SiO₂I-V analysis result chart of (20nm)/n-ZnO heterojunction device.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

Example 1: NiO/SiO with vertical structure₂the/ZnO ultraviolet detector comprises a quartz substrate 1, an ITO electrode layer 2, a NiO film 3 and SiO from bottom to top respectively₂A thin film 4, a ZnO thin film 5 and an Al electrode layer 6.

NiO/SiO with vertical structure₂/ZThe preparation method of the nO ultraviolet detector comprises the following steps:

step 1, substrate cleaning: and (3) carrying out wet cleaning on the quartz substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water according to the volume ratio of 1:1: 3. And heating the solution to 80 ℃ and keeping the temperature for 30min, repeatedly washing the solution by deionized water, and drying the solution by a nitrogen spray gun for later use to remove surface dirt and increase the uniformity and the adhesiveness of the film.

Step 2, sputtering NiO/SiO₂ZnO film: putting the ITO substrate to be cleaned on a substrate table in radio frequency magnetron sputtering equipment, covering a corner area with a mask plate, and vacuumizing the equipment;

the preparation is carried out until the vacuum degree is pumped to 7.0 multiplied by 10^-4Below Pa, setting the sputtering pressure to be 0.6Pa, the sputtering power to be 200W, carrying out timed sputtering for 60min after pre-sputtering for 5min, and firstly preparing a p-NiO thin film layer with the thickness of 130 nm;

setting the sputtering pressure to be 0.8Pa, the sputtering power to be 100W and the sputtering time to be 45min to obtain SiO₂A thin film having a thickness of about 20 nm;

setting the sputtering pressure to be 0.7Pa, the sputtering power to be 200W and the sputtering time to be 70min to obtain the n-ZnO film with the thickness of 100 nm.

Step 3, annealing: and (3) carrying out post-annealing treatment on the prepared film in a tube furnace, keeping the temperature at 600 ℃ for 30min, and increasing the temperature at a rate of 10 ℃/min.

Step 4, evaporating an Al electrode: an Al electrode is vapor-plated on the surface of the n-ZnO by using a mask plate, and the size of the electrode is 2mm multiplied by 2 mm; after the mask plate is removed, silver paste lead-out wires are coated on the reserved ITO substrate and the evaporated Al electrode to be respectively used as a bottom electrode and a top electrode.

FIG. 2 shows the p-NiO/SiO prepared in example 1₂I-V analysis result chart of/n-ZnO heterojunction device.

FIG. 3 is a diagram of the I-V analysis result of the prepared p-NiO/n-ZnO heterojunction ultraviolet photodetector.

The device of fig. 2 of the present invention exhibits better rectification characteristics and low dark current relative to the device of fig. 3. Optimized p-NiO/SiO in FIG. 2₂Dark current of/n-ZnO device under-5V bias voltage is only1.47 muA, rectification ratio-I_dark(+5V)/I_darkThe (-5V) is about 3.45. While the non-optimized p-NiO/n-ZnO device in FIG. 3 has a dark current of 33.67mA at the same bias voltage, which is about 2.3X 10 of the device before optimization⁴Multiple, rectification ratio-I_dark(+5V)/I_darkThe (-5V) is only 1.06. This indicates that SiO₂The addition of the insulating layer can effectively inhibit dark current and improve the rectification ratio so as to optimize the performance of the device. The reason for the rectifying properties and low dark current is the proper thickness of SiO₂The effective addition of an insulating layer. This is due to the fact that microscopic particles, such as electrons, can pass through a "barrier" they cannot otherwise cross, creating a quantum tunneling effect, SiO₂The addition of the insulating layer can form a band gap state between a conduction band and a valence band, so that interface carrier recombination is inhibited, the leakage current is limited and inhibited, and the performance of the device is optimized. The reason for the rectifying characteristics and low dark current is that SiO₂The addition of the insulating layer can effectively inhibit the surface defects of the NiO film and improve the interface performance of p-NiO/n-ZnO, thereby improving the performance of the device.

FIG. 4 shows the p-NiO/SiO prepared in example 1₂The response rate (R) of the/n-ZnO heterojunction ultraviolet photoelectric detector is shown as a graph along with the change of bias voltage. It can be seen that the responsivity of the device increases substantially with increasing bias voltage with a fixed optical power density, reaching a maximum of 8.5 x 10 at 5V bias²mAW^-1。

FIG. 5 shows the p-NiO/SiO₂The detection rate (D) of the/n-ZnO heterojunction ultraviolet photoelectric detector is plotted as a function of bias voltage. It can be seen that under the condition of fixed bias voltage, the detectivity of the device generally increases with the increase of optical power density, and when the optical power density is increased to 2.0mWcm^-2When the bias voltage is small, the value reaches 6.57X 1011cmHz1/2W at the maximum under the micro bias voltage of-0.9V^-1(Jones)。

FIG. 6, FIG. 7 and FIG. 8 show that SiO with different thickness is added under 365nm ultraviolet irradiation₂(7nm, 10nm, 20nm) p-NiO/SiO₂I-V analysis result chart of/n-ZnO heterojunction device, and preparation process and test conditions are the same as example 1. It can be seen that6 medium p-NiO/SiO₂(about 7nm)/n-ZnO heterojunction device can be used for weak ultraviolet light (optical power density of 0.7 mWcm)^-2) There is almost no response and the I-V curve appears linear, indicating that no heterojunction is formed at this time. When SiO as shown in FIG. 7₂When the thickness of the insulating layer is increased to 10nm, the I-V curve shows good rectifying behavior, and shows positive on and reverse off under dark conditions without illumination, and the dark current is 34 muA under a bias voltage of-2V. While in FIG. 8 p-NiO/SiO₂The dark current of the (20nm)/n-ZnO heterojunction device under the same bias voltage is only 44nA, which is nearly three orders of magnitude lower than that in FIG. 7, and the dark current under the bias voltage of-5V is as low as 1.47 muA, and the increase of the photocurrent under the illumination condition is more obvious. This indicates that only a suitable thickness of SiO is added between the two materials₂The insulating layer can achieve the purpose of optimizing the performance of the device, and the SiO is too thin₂The layer cannot effectively suppress the dark current of the device so as to improve important performance parameters such as light-dark current ratio, rectification ratio and the like. Therefore, SiO with the thickness of about 20nm is selected in the invention₂The layer regulates and controls the structure of the device to prepare p-NiO/SiO with a simple vertical structure₂the/n-ZnO heterojunction ultraviolet photoelectric detector.

Example 2: NiO/SiO with vertical structure₂The preparation method of the/ZnO ultraviolet detector comprises the same steps as the example 1 and the step 2, and NiO/SiO sputtering is carried out₂The ZnO film specifically comprises:

putting the ITO substrate to be cleaned on a substrate table in radio frequency magnetron sputtering equipment, covering a corner area with a mask plate, and vacuumizing the equipment;

the preparation is carried out until the vacuum degree is pumped to 7.0 multiplied by 10^-4Below Pa, setting the sputtering pressure to be 0.8Pa, the sputtering power to be 220W, timing and sputtering for 70min after pre-sputtering for 5min, and firstly preparing a p-NiO thin film layer with the thickness of 150 nm;

setting the sputtering pressure to be 0.8Pa, the sputtering power to be 100W and the sputtering time to be 35min to obtain SiO₂A thin film having a thickness of about 10 nm;

setting the sputtering pressure to be 0.9Pa, the sputtering power to be 220W and the sputtering time to be 80min to obtain the n-ZnO film with the thickness of 120 nm.

Example 3: NiO/SiO with vertical structure₂The preparation method of the/ZnO ultraviolet detector comprises the same steps as the example 1 and the step 2, and NiO/SiO sputtering is carried out₂The ZnO film is specifically as follows:

putting the ITO substrate to be cleaned on a substrate table in radio frequency magnetron sputtering equipment, covering a corner area with a mask plate, and vacuumizing the equipment;

the preparation is carried out until the vacuum degree is pumped to 7.0 multiplied by 10^-4Below Pa, setting the sputtering pressure to be 0.6Pa, the sputtering power to be 180W, timing and sputtering for 50min after pre-sputtering for 5min, and firstly preparing a p-NiO thin film layer with the thickness of 110 nm;

setting the sputtering pressure to be 0.8Pa, the sputtering power to be 80W and the sputtering time to be 35min to obtain SiO₂A thin film having a thickness of about 7 nm;

setting the sputtering pressure to be 0.7Pa, the sputtering power to be 180W and the sputtering time to be 60min to obtain the n-ZnO film with the thickness of 80 nm.

Claims (4)

1. NiO/SiO with vertical structure₂the/ZnO ultraviolet detector is characterized in that the functional layer of the detector is NiO/SiO₂/ZnO, adding SiO between p-ZnO and n-ZnO heterojunction₂An insulating layer.

2. The vertical structure NiO/SiO of claim 1₂the/ZnO ultraviolet detector is characterized by comprising a quartz substrate, an ITO electrode layer, a NiO film and SiO from bottom to top respectively₂Thin film, ZnO thin film and Al electrode layer.

3. NiO/SiO with vertical structure₂The preparation method of the/ZnO ultraviolet detector is characterized by comprising the following steps:

step 1, substrate cleaning: carrying out wet cleaning on the quartz substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water according to the volume ratio of 1:1: 3;

step 2, sputtering NiO/SiO₂ZnO film: sequentially carrying out radio frequency magnetron sputtering on NiO and SiO on an ITO substrate₂And a ZnO film; the vacuum degree of the equipment is pumped to 7.0 multiplied by 10^-4Pa below;

setting the sputtering pressure at 0.6-0.8Pa, the sputtering power at 180-;

setting the sputtering pressure at 0.8-1.0Pa, the sputtering power at 80-120W and the sputtering time at 35-55min to obtain SiO₂A thin film having a thickness of about 5 to 22 nm;

setting the sputtering pressure at 0.7-0.9Pa, the sputtering power at 180-220W and the sputtering time at 60-80min to obtain the n-ZnO film with the thickness of 80-120 nm.

Step 3, annealing: the prepared film is annealed in a tube furnace at 500-600 ℃ for 25-35min at the heating rate of 8-10 ℃/min.

Step 4, evaporating an Al electrode: and (4) evaporating and plating an Al electrode on the surface of the n-ZnO.

4. The vertical structure NiO/SiO of claim 1₂the/ZnO ultraviolet detector is characterized in that the SiO₂And the thickness of the film is about 20 nm.

Images