CN108802152A - A kind of compound organic nano-crystal field-effect transistor gas sensor preparation method of polymer/oxide - Google Patents

Abstract

The invention relates to a method for preparing a polymer/oxide composite organic nanocrystal field-effect transistor gas sensor, in which a substrate (1) is covered with an oxide layer (2) of silicon dioxide and a polymer layer (3) to form a composite insulation Layer, the polymer layer protects the _oxide layer, so that NO2 molecules will not be deeply trapped in the silicon _dioxide , which is conducive to the desorption of NO2 molecules. The titanium dioxide solution is made into a thin film by spin coating as the oxide buffer layer (4), and hexathiophene columnar nanocrystals are formed by vacuum deposition and growth on the oxide buffer layer (4) at fast, slow, and fast evaporation rates. An organic nanocrystalline layer (5), and then continue to spin-coat an oxide buffer layer (6), and finally vapor-deposit a gold electrode (8). The _oxide buffer layer greatly increases the electron transport rate and improves the sensitivity and responsiveness to NO2 molecules. The organic nanocrystalline layer composed of hexathiophene columnar nanocrystals has the characteristics of three-dimensional adsorption and desorption, which improves the sensitivity of the sensor.

Description

A Polymer/Oxide Composite Organic Nanocrystalline Field-Effect Transistor Gas Sensor Preparation

technical field

The invention relates to a method for preparing a polymer/oxide composite organic nanocrystal field effect transistor gas sensor, belonging to the field of organic semiconductors.

Background technique

Due to serious air pollution, environmental monitoring with gas sensors is very meaningful. Nitrogen dioxide (NO ₂ ) is the main pollutant caused by burning fuel, which may cause photochemical smog, acute pneumonia, acid rain, edema and eye inflammation, and may even cause cancer. Inorganic _NO2 sensors are usually bulky, have low selectivity and high power consumption. Therefore, it is of great importance to develop novel gas sensors with high sensitivity and selectivity, light weight, and low power consumption.

The organic field effect transistor sensor is a new type of gas sensor that uses organic semiconductors as the active layer. On the one hand, organic field-effect transistor sensors, a key component of modern electronics, have significant advantages over inorganic gas sensors in terms of molecular design diversity, low cost, light weight, mechanical flexibility, and low operating voltage. On the other hand, organic field-effect transistor sensors are considered to be an important solution for high-quality organic thin film environmental monitoring.

Therefore, in the present invention, the polymer PVP solution is spin-coated on the silicon dioxide SiO ₂ insulating layer to form a polymer/ _{oxide composite insulating layer, which reduces the adsorption of NO molecules in the SiO 2 insulating} layer, and optimizes the detection of gas NO. ₂ Molecular adsorption/desorption process. A hexathiophene organic nanocrystal layer with a columnar structure was prepared by fast, slow, and fast continuous evaporation rates to achieve three _- dimensional adsorption of NO molecules. And by increasing the oxide buffer layer structure to reduce the contact surface resistance, the carrier transport rate is greatly optimized, which is conducive to the highly sensitive reaction to _NO2 molecules and the rapid recovery of the sensor.

Contents of the invention

The invention provides a method for preparing a polymer/oxide composite organic nanocrystal field effect transistor gas sensor. The structure of the polymer/oxide composite organic nanocrystalline field effect transistor is shown in Figure 1. The composite insulating layer covered on the substrate (1) includes an oxide layer (2), a PVP polymer layer (3), the oxide layer ( ₂ ) is composed of SiO2, and has a thickness between 200-220 nm. Dissolve PVP with ethanol solvent to make a solution with a concentration of 5 mg/ml, and then use the spin coating method at room temperature to make a polymer layer (3 ), with a thickness between 200 and 300 nm. The polymer layer (3) of PVP has a dense structure and has a protective effect on the oxide layer ( ₂ ), so that NO2 molecules will not be deeply trapped in the oxide layer (2). The _TiO2 powder was dissolved in ethanol solvent to make a solution with a concentration of 2 mg/ml. At room temperature, the spin coating method was used to make a thin film under the conditions of forward rotation of 500 r and 6 s, and back rotation of 1800 r and 30 s. The thickness is between 50 and 100 nm, as oxide buffer layers (4) and (6), which reduce the resistance of the contact surface and increase the carrier transport rate.

At a substrate temperature of 90°C and a vacuum of 8×10 ^-4 Pa, a hexathiophene organic nanocrystalline layer (5) was grown on the oxide buffer layer (4) with a thickness of 20 nm, successively at a rapid rate of 0.5-1 nm /min, slow 0.1-0.2 nm/min, and fast 0.5-1nm/min vapor deposition rates for 10 min, 60 min, and 10 min, respectively, to form hexathiophene columnar nanocrystals, forming an organic nanocrystalline layer (5). It has a columnar structure, which increases the contact area with NO2 molecules, thereby realizing the _{three -} dimensional adsorption of NO2 molecules, which is conducive to the highly sensitive reaction to _NO2 molecules and the rapid recovery of the sensor. Finally, a gold electrode (8) is vacuum-evaporated on the oxide buffer layer (6) to form a polymer/oxide compound organic nanocrystal field effect transistor gas sensor.

The NO ₂ molecules (9) first contact with the oxide buffer layer (6) to react, and the electrons (7) are transferred. Due to the charge transfer effect, the electrons (7) are transferred to the organic nanocrystalline layer through the oxide buffer layer (6) (5), and then transferred between the organic nanocrystalline layer (5) and the oxide buffer layer (4). The oxide buffer layer (4), (6) greatly increases the carrier transport rate, and the columnar organic nanocrystalline layer can efficiently adsorb NO2 molecules, thus enabling highly sensitive reactions and sensors for NO2 molecules ( _{9 )} quick recovery. The invention is beneficial to improve the fast response and fast recovery of the organic sensor.

Description of drawings

Figure 1. Structural diagram of polymer/oxide composite organic nanocrystalline field-effect transistor gas sensor.

Detailed ways

A specific realization process of a method for preparing a polymer/oxide composite organic nanocrystal field-effect transistor gas sensor: chemical vapor deposition of silicon dioxide (SiO ₂ ) on a substrate (1) with a thickness of 200 nm. Polyvinylpyrrolidone (PVP) solution was spin-coated to form the polymer layer (3), ethanol was used as the solvent, the concentration of the solution was 5 mg/ml, and the spin-coating conditions were forward rotation 400 r, 6 s, back rotation 1300 r, 30 s , with a thickness of 260 nm. Titanium dioxide (TiO ₂ ) solution was spin-coated to form oxide buffer layers (4) and (6), using ethanol solvent, the solution concentration was 2 mg/ml, and the spin-coating conditions were 500 r for 6 s, 1800 for back spin r, 30 s, the thickness is 60 nm. Under the vacuum degree of 8×10 ^-4 Pa, the substrate temperature is 90 ℃, and the thickness is 20 nm. The deposition rates are respectively fast 0.5 nm/min, slow 0.1 nm/min, and fast 0.5 nm/min. Hexathiophene (α-6T) was deposited continuously for 10 min, 60 min, and 10 min to form columnar nanocrystals to form an organic nanocrystalline layer (5), and finally a 30 nm gold electrode (8) was evaporated.

Claims (4)

1. A method for preparing a polymer/oxide composite organic nanocrystalline field-effect transistor gas sensor comprising: a substrate (1), a composite insulating layer including an oxide layer (2), a polymer layer (3), and an oxide buffer layer (4), an organic nanocrystalline layer (5), an oxide buffer layer (6), and an electrode (8). 2. A method for preparing a polymer/oxide composite organic nanocrystalline field effect transistor gas sensor according to claim 1, characterized in that the oxide layer (2) in the composite insulating layer is made of silicon dioxide (SiO ₂ ), The thickness is between 200-220 nm; the polymer layer (3) is made by spin-coating polyvinylpyrrolidone (PVP) solution, using ethanol solvent, the solution concentration is 5mg/ml, and the spin-coating conditions are forward rotation 400 r, 6 s , then turn to 1300 r, 30 s, and the thickness is between 200 nm and 300 nm. 3. A method for preparing a polymer/oxide composite organic nanocrystalline field effect transistor gas sensor according to claim 1, characterized in that the oxide buffer layers (4) and (6) are made of titanium dioxide (TiO ₂ ) solution spin It is made by coating with ethanol solvent, the solution concentration is 2 mg/ml, the spin coating conditions are 500 r for 6 s, 1800 r for 30 s, and the thickness is between 50 nm and 100 nm. 4. A method for preparing a polymer/oxide composite organic nanocrystalline field effect transistor gas sensor according to claim 1, characterized in that the organic nanocrystalline layer (5) is made of hexathiophene (α-6T) at 8×10 ^-4 Pa, the substrate temperature is 90 ℃, and the thickness is 20 nm. The deposition rate was 10 min, 60 min, and 10 min, respectively, to form columnar nanocrystals.