CN102321917A

CN102321917A - Preparation method for Si-doped alpha-Fe2O3 super-lattice nanostructure

Info

Publication number: CN102321917A
Application number: CN201110164389A
Authority: CN
Inventors: 梁长浩; 刘俊; 张和民; 田振飞
Original assignee: Hefei Institutes of Physical Science of CAS
Current assignee: Hefei Institutes of Physical Science of CAS
Priority date: 2011-06-18
Filing date: 2011-06-18
Publication date: 2012-01-18

Abstract

The invention discloses a preparation method for a Si-doped alpha-Fe2O3 super-lattice nanostructure. Silicon sol solution which is obtained by using a liquid-phase laser ablation technology is uniformly mixed with FeCl3 solution to react at the temperature of 175-185 DEG C for 10-14 hours so as to obtain the Si-alpha-Fe2O3 super-lattice nanostructure. On one hand, the application of the liquid-phase laser ablation technology in material synthesis is expanded; and on the other hand, the influence of doping on semiconductor materials is deeply researched and new approach and material basis are provided.

Description

Si doped alpha-Fe 2O 3The preparation method of superlattice nanostructure

Technical field

The present invention relates to a kind of nanometer α-Fe ₂O ₃The preparation method of structure is specifically related to Si doped alpha-Fe ₂O ₃The preparation method of superlattice nanostructure.

Background technology

α-Fe with low energy gap width ₂O ₃(2.1-2.2eV) and broad stopband TiO ₂(～3.2eV) is two kinds of maximum materials of present energy and material and photocatalysis field research.But two kinds also all exist material intrinsic inherent defective when having numerous advantages, like α-Fe ₂O ₃Narrower owing to being with, can absorb the sunshine about 40%, but also make the recombination rate of photohole-electronics accelerate simultaneously.And TiO ₂Can be with broad, the recombination rate of photohole-electron pair is than α-Fe ₂O ₃Slow is many, but the scope of its photoabsorption concentrates on ultraviolet region, therefore low to the absorption rate of sunshine.Given this, for the defective of these materials own, people have adopted a lot of methods to carry out modification to promote its opto-electronic conversion performance.Adopt maximum means to have two kinds, the one, the material structure nanometer, surface effects that nano material is brought and quantum size effect make a lot of rerum naturas of material that huge change take place, such as energy gap etc.; The 2nd, mix, doping different impurity element can improve the concentration of current carrier on the one hand in semiconductor material, can produce shallow impurity level on the other hand, has stoped the compound of photohole-electron pair to a certain extent.With α-Fe ₂O ₃Be example, when its during as the anode material of photodissociation water, because α-Fe ₂O ₃Photohole diffusion length very short, be merely about 5nm, make the light induced electron hole-recombination accelerate, reduced photoelectric transformation efficiency.And α-Fe ₂O ₃Resistance bigger, further limited its application in the opto-electronic conversion field.If at α-Fe ₂O ₃In other impurity atomss that successfully mix, can improve its resistivity effectively and reduce the compound of hole-electron pair, thereby strengthen the opto-electronic conversion performance.For the doping of semiconductor material, using maximum adulterating methods at present has chemical Vapor deposition process, magnetron sputtering method, and technique for atomic layer deposition etc.

Summary of the invention

The object of the invention is to provide a kind of Si doped alpha-Fe ₂O ₃The preparation method of superlattice nanostructure.

The present invention adopts following technical scheme to achieve these goals:

Si doped alpha-Fe ₂O ₃The preparation method of superlattice nanostructure is characterized in that may further comprise the steps:

(1) the elementary silicon target is immersed in the deionized water, adopted Nd:YAG pulse laser ablation elementary silicon target 25-35 minute, obtain colloidal silica solution, then with colloidal silica solution with contain 4-5.5mmol FeCl ₃Solution mixes;

(2) with colloidal silica solution and FeCl ₃The solution mixing solutions changes in the teflon-lined autoclave, reacts 10-14h, the Si-α-Fe that promptly obtains down at 175-185 ℃ ₂O ₃The superlattice nanostructure.

Described Si doped alpha-Fe ₂O ₃The preparation method of superlattice nanostructure is characterized in that described Nd:YAG pulse laser wavelength is 1064nm, and energy is 70mJ.

The present invention unites use liquid laser ablation technology and hydrothermal technique first, designs and successfully synthesize to have superstructure Si doped alpha-Fe ₂O ₃, just a kind of special orderly dopant material, and set up the corresponding structure model, thus to study foreign atom be how to influence α-Fe for the physical model of setting up coupling is simulated ₂O ₃The opto-electronic conversion performance foundation is provided.Si doped alpha-Fe ₂O ₃Superlattice nanometer sheet building-up process is roughly following: at first utilize the liquid laser ablation technology to synthesize the silicon sol with high reaction activity.Then with silicon sol and FeCl ₃Solution mixes, and can obtain having the α-Fe of the silicon doping of superstructure through hydrothermal treatment consists ₂O ₃One aspect of the present invention has been expanded the liquid laser ablation technology in the application of material aspect synthetic, and the influence of also mixing to semiconductor material for further investigation on the other hand provides new approach and foundation.

Description of drawings

Fig. 1 liquid laser ablation technology and hydro-thermal reaction coproduce have the doped semiconductor schema of superstructure.

α-the Fe of Fig. 2 silicon doping ₂O ₃Low magnification SEM photo (a) and TEM photo (b).

α-the Fe of Fig. 3 silicon doping ₂O ₃The high resolution TEM photo (a-b) of ultrathin nanometer sheet; (c) be the electron diffraction spot; (d) be entrained in α-Fe for Siliciumatom ₂O ₃Two-dirnentional structure model in the lattice is along the axial projection of c.

The pure phase α of Fig. 4-Fe ₂O ₃α-Fe with silicon doping ₂O ₃Ultraviolet-visible photoabsorption collection of illustrative plates.

Embodiment

Embodiment 1:

α-Fe with silicon doping of superstructure ₂O ₃Synthetic as shown in Figure 1, A is that purity is that 99.999% elementary silicon target is immersed in the 20ml deionized water, adopts the Nd:YAG pulse laser, and wavelength is 1064nm, and energy is 70mJ, ablation elementary silicon target half a hour.The colloidal silica solution and the FeCl of preparation gained ₃Solution (contains 5mmol FeCl ₃) mix, change over to then in the teflon-lined autoclave, react 12h down at 180 ℃, can obtain the α-Fe of the silicon doping of good dispersibility ₂O ₃Doped semiconductor.

Fig. 2 (a) is the α-Fe of silicon doping ₂O ₃Low power SEM photo, can find out that product is made up of the nanometer sheet of a large amount of even size distribution, the diameter of nanometer sheet can know that by Fig. 2 (b) thickness of nanometer sheet is about 10nm in the 80-95nm scope, this can remedy α-Fe to a certain extent ₂O ₃The shortcoming that hole diffusion length is short is a kind of embodiment of nano-structured effect.

Fig. 3 (a) is α-Fe that the present invention prepares the silicon doping of gained ₂O ₃The TEM photo of ultrathin nanometer sheet, shown in three rectangle marked among the figure, along [210], all there is the formation of superlattice striped in [120] and [110] crystal orientation.This result with shown in Fig. 3 c to choose the result that the electron diffraction spot calculates out consistent.Formed different superlattice stripeds on three directions have been comprised especially at illustrated delta-shaped region.Be further research; We have provided the high-resolution TEM photo of delta-shaped region; Shown in Fig. 3 (b); Because the valence electron of Siliciumatom and Pauling radius and iron atom be difference to some extent,, therefore can very clearly see the superlattice crystal face of formation and the particular location of alloying element so on substituted position, local lattice distortion can take place.Can draw through measuring, the basic crystal face among Fig. 3 (b) is (110), and spacing is 0.251nm.On three directions shown in above-mentioned, have the superlattice crystal face forms, the formation of superlattice crystal face is also arranged on [110] crystal orientation.We can clearly count and whenever a superlattice crystal face will occur at a distance from 9 (110) crystal faces, are defined as pl, and its spacing d1 is 2.51nm.Illustrated superlattice crystal face p2 forms along [210] crystal orientation, and through whenever superlattice crystal face p2 occurring at a distance from 14 (300) crystal faces to calculating of SEAD spot (Fig. 3 (c)), its spacing is 2.17nm.But because the spacing too little (being merely 0.145nm) of (300) crystal face, and observe between can not be in this high resolution TEM photo.Fig. 3 (d) is the α-Fe of silicon doping ₂O ₃The space model figure of superstructure demonstrates the different superlattice faces that comprise in the above-mentioned picture.The representative of green bead is Siliciumatom among the figure, replaced the part iron atom in the lattice (shown in the white bead), and formed a bigger lattice, this with choose the result that the electron diffraction spot drawn and fit like a glove.In addition, marked among the figure along the superlattice face pl of [110] direction appearance and the superlattice face p2 that occurs along [210] direction, several relations of corresponding spacing d1 and d2 are consistent with the result that Fig. 3 b measures.According to α-Fe ₂O ₃Trigonal system symmetry we can also learn that along [210] or [110] direction, whenever a superlattice face will occur at a distance from 14 (030) or (330), the spacing of these superlattice faces is consistent with d2.

Fig. 4 is pure phase α-Fe ₂O ₃α-Fe with silicon doping ₂O ₃Uv absorption spectra.Compare and to know, the α-Fe of silicon doping ₂O ₃The absorption peak of (red curve) is with respect to pure phase α-Fe ₂O ₃Tangible red shift has taken place in (black curve).This is because the result that the shallow energy level that quantum size effect and Siliciumatom doping are produced is brought.The Siliciumatom formed shallow energy level of mixing not only can provide majority carrier and can also slow down the compound of photohole-electron pair, and the raising that this is expected to realize the utilization ratio of sunshine improves light conversion efficiency effectively.

Claims

1.Si doped alpha-Fe ₂O ₃The preparation method of superlattice nanostructure is characterized in that may further comprise the steps:

(2) with colloidal silica solution and FeCl ₃The mixing solutions of solution changes in the teflon-lined autoclave, reacts 10-14h, the Si-α-Fe that promptly obtains down at 175-185 ℃ ₂O ₃The superlattice nanostructure.

2. Si doped alpha-Fe according to claim 1 ₂O ₃The preparation method of superlattice nanostructure is characterized in that described Nd:YAG pulse laser wavelength is 1064nm, and energy is 70mJ.