CN100557770C - A method for preparing GaMnN dilute magnetic semiconductor nanowires - Google Patents

Abstract

The invention discloses a kind of method of the GaMnN of preparation diluted magnetic semiconductor nano-line.The inventive method comprises the steps: 1) the Mn doping: at Ga ₂O ₃In-situ doped Mn on the nano wire; 2) ammonification: the Ga that will be mixed with Mn ₂O ₃Nano wire carries out ammonification under ammonia atmosphere, obtain the GaMnN diluted magnetic semiconductor nano-line.The inventive method is simple, lower to equipment requirements, prepared GaMnN nano wire has very strong ferromagnetism, Curie temperature is higher than room temperature, and its magnetic-doped concentration is controlled, nano wire purity height, output is big, linear controlled growth parameter(s)s such as (regulate can prepare the nano wire of diameter tens nanometers) air pressure to the hundreds of nanometer, can be used for spin field effect triode (spin-FET), spinning LED (spin-LED), the manufacturing of spin resonance tunneling device nanometer spin electric devices such as (spin-RTD) has broad application prospects.

Description

A method for preparing GaMnN dilute magnetic semiconductor nanowires

technical field

The invention relates to a method for preparing nanowires, in particular to a method for preparing GaMnN dilute magnetic semiconductor nanowires.

Background technique

The room temperature ferromagnetism of dilute magnetic semiconductor materials is an important property of whether it can be used in the manufacture of spintronic devices. As a wide bandgap semiconductor material, GaN has excellent optical and electrical properties. In theory, GaN doped with Mn will make It has a ferromagnetic order higher than room temperature, so GaMnN dilute magnetic semiconductor materials are current research hotspots. However, due to the low solid solubility of magnetic ions in semiconductors, it is still very difficult to prepare highly doped GaMnN dilute magnetic semiconductor materials with Mn replacing lattice cations by traditional methods. Moreover, it has been reported in the literature that using the above method If the doping concentration of Mn in GaN is greater than 3 at.% during preparation, Mn ions will fill in the lattice gap instead of replacing Ga, thus forming Ga _x Mn _y grains, which will affect the magnetic properties of the material. Magnetic impurity phase precipitation problem. Deepak et al. (FLDeepak, PU Vanitha, A. Fovindaraj, CNRRao, Chem. Phys. Lett. 374 (2003) 314) used carbon nanotubes as a template to prepare GaMnN dilute magnetic semiconductor nanowires, but the yield of samples was less.

Contents of the invention

The purpose of the present invention is to provide a method for preparing GaMnN dilute magnetic semiconductor nanowires.

The method for preparing GaMnN dilute magnetic semiconductor nanowires provided by the present invention comprises the following steps:

1) Mn doping: Ga ₂ O ₃ nanowires are in-situ doped with Mn;

2) Ammonification: the Ga ₂ O ₃ nanowires doped with Mn are ammonified in an ammonia atmosphere to obtain GaMnN dilute magnetic semiconductor nanowires.

Wherein, the conditions _for in-situ doping Mn on _Ga2O3 nanowires in step 1) are:

Put the MnCl ₂ ·4H ₂ O powder, gallium source substrate and collection substrate in turn into a quartz boat with one end open, then put the quartz boat into the tube furnace, and make the open end face the airflow direction; closed system, Vacuumize, then pass in argon for cleaning, control the pressure in the furnace to 0.6-0.9 standard atmospheric pressure, and pass in argon as a carrier gas; and set the heating rate at 15-20°C/min, so that the temperature of the tube furnace rises to Keep the temperature at 900°C, and obtain Ga ₂ O ₃ nanowires doped with Mn on the collecting substrate.

Under the above temperature and pressure conditions, Ga ₂ O ₃ nanowires are grown on the collection substrate. Moreover, during the growth process of Ga ₂ O ₃ nanowires, due to the continuous decomposition of manganese chloride and the transport of the carrier gas flow, manganese enters the crystal lattice of Ga ₂ O ₃ to achieve Mn doping. The doping concentration of Mn can be controlled by putting in different amounts of MnCl ₂ ·4H ₂ O powder and its relative positions with the source substrate and the collection substrate.

Step 2) the described condition of carrying out ammoniation is:

Raise the temperature of the furnace to 1050°C, turn off the argon gas, pass through the ammonia gas and keep it warm for 40 minutes, and control the pressure to 0.9 atmospheric pressure, and perform ammoniation treatment on the Mn-doped Ga ₂ O ₃ nanowires to obtain the GaMnN dilute magnetic semiconductor Nanowires.

GaMnN dilute magnetic semiconductor nanowires with different Mn doping concentrations can be obtained according to the different doping concentrations of Mn in the Ga ₂ O ₃ nanowires. In addition, after the ammonification treatment, in order to prevent the nanowires from being oxidized, argon gas must be introduced after the ammonia gas is turned off, and the temperature is naturally lowered to room temperature, so that GaMnN dilute magnetic semiconductor nanowires grow on the Si substrate.

The present invention uses the oxide ammonification method to prepare GaMnN dilute magnetic semiconductor nanowires (DMS NWs), which is mainly divided into _two steps: the first step is to perform Mn doping in situ during the growth stage of _Ga2O3 nanowires, Because of the high solid solubility of Mn in the oxygallium manganese system, a higher concentration of Mn doping can be obtained; then in the second step, ammoniation treatment is carried out under a high-temperature ammonia atmosphere, and nitrogen atoms gradually replace the lattice positions of oxygen atoms , making the nanowires gradually transform into GaMnN nanowires. During the preparation process, Mn atoms are frozen in the GaN lattice structure, which prevents the precipitation of magnetic Mn ions, thereby avoiding the problem of magnetic impurity phase precipitation caused by Mn doping of GaN materials by conventional methods. Structural analysis shows that the GaMnN nanowire prepared by the method of the invention has a single hexagonal GaN crystal structure without magnetic impurity phases; magnetic measurement shows that the GaMnN nanowire has ferromagnetism at room temperature, and the Curie temperature is at least higher than room temperature. The method of the present invention is simple, requires less equipment, and can be carried out by using an ordinary tube furnace; the prepared GaMnN nanowire has strong ferromagnetism, the Curie temperature is higher than room temperature, and its magnetic doping concentration is controllable, which can The magnetic properties and Curie temperature of sample nanowires can be controlled by changing the doping concentration of manganese and nitrogen in the sample; the nanowires have high purity, large output, and controllable line shape (adjusting growth parameters such as gas pressure can prepare tens of nanometers to hundreds of nanometers in diameter) nanowires), which can be used in the manufacture of spin-field-effect transistors (spin-FETs), spin-light-emitting diodes (spin-LEDs), spin-resonance tunneling devices (spin-RTDs) and other nano-spintronic devices, with Broad application prospects.

Description of drawings

Fig. 1 is the scanning electron microscope picture of nanowire;

Fig. 2 is the X-ray diffraction spectrum of nanowire;

Fig. 3 is the analysis photograph of nanowire;

Figure 4 is the M-H curve of the nanowire at room temperature.

Detailed ways

Embodiment 1,

1. GaMnN dilute magnetic semiconductor nanowires were prepared in large quantities by oxide ammoniation method.

A Si chip coated with a 5nm gold film was used as the collection substrate of the product, and a small ceramic cup filled with MnCl ₂ 4H ₂ O powder, a gallium source substrate (a Si chip with 100 mg of metal gallium placed on it) and three collection substrates were used. The substrates are placed in a quartz boat with one end open in turn, and the small ceramic cup is about 10cm away from the gallium source substrate. Then place the quartz boat in the center of the tube furnace with the open end facing the direction of the airflow. After closing the system, turn on the mechanical pump to evacuate to a vacuum, pass in argon gas for cleaning, and raise the system pressure to normal pressure, and repeat this three times. After the experiment started, the required pressure (0.6-0.9 standard atmospheric pressure) was maintained by manually controlling the needle valve, and the heating curve was set (heating rate: 15-20° C./min). Introduce 80 sccm argon as the carrier gas, raise the temperature of the tube furnace to 900°C within 50 minutes, and keep it for 30 minutes; then directly raise the furnace temperature to 1050°C, turn off the argon, feed ammonia and keep it warm for 40 minutes Minutes, control the pressure to be 0.9 atmospheric pressure, and carry out nitrogen doping; after the ammoniation treatment is completed, turn off the ammonia gas and feed argon gas 80sccm, and naturally cool down to room temperature, that is, GaMnN dilute magnetic semiconductor nanowires grow on the Si substrate, by This prepared sample A and sample B with different Mn doping concentrations.

The sample is expressed in the following way: ammoniation temperature/ammoniation time/ammonia gas flow/put MnCl ₂ 4H ₂ O amount/Mn concentration (at.% is the atomic percentage concentration), the sample A obtained in the above examples : 1050°C/40min/100sccm/0.80g/4at.%); Sample B: 1050°C/40min/100sccm/1.1g/8at.%.

2. Morphology, structure and magnetic analysis of GaMnN dilute magnetic semiconductor nanowires

1. Appearance and size

The scanning electron microscope image of the nanowires is shown in Figure 1. The results show that a large number of nanowires are grown on the silicon substrate. The average diameter of the nanowires is about 100 nm and the length is about tens of microns.

2. Crystal phase

X-ray diffraction of the obtained nanowires shows that the crystal phase is a hexagonal phase (wurzite), and there is no magnetic impurity phase, as shown in FIG. 2 .

3. Structural analysis

Figure 3a and Figure 3b are TEM low-resolution images of nanowires (sample A) and 8at.% nanowires (sample B) with a Mn doping concentration of 4at.% respectively; the electron diffraction spectrum of sample A nanowires is shown in Figure 3c As shown in Figure 3d (corresponding to two different nanowires in sample A), the electron diffraction spectrum of sample B nanowires is shown in Figure 3e and Figure 3f (corresponding to two different nanowires in sample B), corresponding to [0001] Axis electron diffraction, the lattice structure can be calibrated as a hexagonal wurtzite GaN structure; Figure 3g and Figure 3h are high-resolution transmission images of nanowires with Mn doping concentrations of 4at.% and 8at.%, respectively.

)与纳米线的电子衍射分析得到的晶格常数差别很大，也表明在所制备的纳米线中同样不存在GaMn₃晶型结构，本发明所制备的GaMnN纳米线具有单一的GaN相结构。高分辨透射图像(图2g、图2h)中清晰的条纹像表明纳米线具有单晶结构，纳米线表面干净而且结构完整，进一步证实在GaMnN纳米线中Mn离子掺入到了GaN晶格结构中，而不是以Mn的析出相或Mn的杂质相形式存在于纳米线中：对Mn掺杂浓度4at.％的纳米线，条纹像间距为0.244nm，对应于六角GaN结构(-1 01 1)面的面间距；对Mn掺杂浓度8at.％的纳米线，条纹像间距为0.276nm，对应于GaN结构(1 0 -1 1)面间距。From the above results, it can be seen that the electron diffraction spots of the obtained nanowires all present the six-fold symmetry corresponding to the hexagonal GaN structure, and there are no diffraction spots of other impurity phases such as four-fold symmetry, which indicates that there is no tetragonal (Mn ₃ N ₂ , MnN, GaMn, Ga _0.4 Mn _0.6 ) or cubic (Mn ₄ N, Mn, Ga _7.7 Mn _2.3 , Ga ₅ Mn ₈ ) impurity phases, and since none of the Mn oxides has a hexagonal structure, it means that nanowires also have There is no Mn oxide impurity phase; in addition, no diffraction peak corresponding to _GaMn3 is found in the XRD spectrum of the nanowire, and the lattice constant of _GaMn3 (

) is very different from the lattice constant obtained by the electron diffraction analysis of the nanowire, which also shows that there is no GaMn ₃ crystal structure in the prepared nanowire, and the GaMnN nanowire prepared by the present invention has a single GaN phase structure. The clear fringe images in the high-resolution transmission images (Figure 2g, Figure 2h) indicate that the nanowires have a single crystal structure, and the surface of the nanowires is clean and structurally complete, which further confirms that Mn ions are incorporated into the GaN lattice structure in the GaMnN nanowires, It does not exist in the nanowires in the form of Mn precipitates or Mn impurity phases: for nanowires with a Mn doping concentration of 4at.%, the fringe image spacing is 0.244nm, corresponding to the hexagonal GaN structure (-1 01 1) plane The interplanetary spacing; for nanowires with a Mn doping concentration of 8at.%, the fringe image spacing is 0.276nm, corresponding to the GaN structure (1 0 -1 1) interplanetary spacing.

4. Magnetic measurement

The M-H curve of the nanowire with a Mn doping concentration of 8at.% at room temperature is shown in Figure 4. It can be seen from the figure that the nanowire still has an obvious hysteresis loop at room temperature, and the coercive force reaches 1270e, which is clear It shows that the GaMnN nanowire of the present invention exists ferromagnetic state at room temperature, has room temperature ferromagnetism, and the Curie temperature is at least higher than room temperature.

Claims (2)

1. A method for preparing GaMnN dilute magnetic semiconductor nanowires, comprising the steps of: 1) Mn doping: doping Mn in situ on Ga ₂ O ₃ nanowires; the conditions for doping Mn in situ on Ga ₂ O ₃ nanowires are: MnCl ₂ 4H ₂ O powder, gallium source The substrate and the collecting substrate are placed in a quartz boat with an open end in turn, and then the quartz boat is put into the tube furnace with the open end facing the direction of the air flow; the system is closed, vacuumed, and then argon gas is introduced for cleaning. Control the pressure in the furnace to 0.6-0.9 standard atmospheric pressure, feed argon as the carrier gas; and set the temperature rise rate to 15-20°C/min, so that the temperature of the tube furnace rises to 900°C, keep the temperature, and collect _Ga2O3 nanowires doped with Mn _were obtained 2) Ammonification: the Ga ₂ O ₃ nanowires doped with Mn are ammonified in an ammonia atmosphere to obtain GaMnN dilute magnetic semiconductor nanowires. 2. The method according to claim 1, characterized in that: the conditions for ammoniation are as follows: raise the furnace temperature to 1050°C, turn off the argon gas, feed ammonia gas and keep it warm for 40 minutes, and control the pressure to 0.9 Atmospheric pressure, the Ga ₂ O ₃ nanowires doped with Mn are subjected to ammonification treatment to obtain GaMnN dilute magnetic semiconductor nanowires.

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