CN1736871A - Method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip - Google Patents
Method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip Download PDFInfo
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- CN1736871A CN1736871A CN 200510021182 CN200510021182A CN1736871A CN 1736871 A CN1736871 A CN 1736871A CN 200510021182 CN200510021182 CN 200510021182 CN 200510021182 A CN200510021182 A CN 200510021182A CN 1736871 A CN1736871 A CN 1736871A
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Abstract
The method to epitaxial grow magnesia nano line on single crystal substrate of strontium titanate relates to micro-electronics material field particular to the application on hetero epitaxy center nano line and its periodic surface structure of oxide (magnesis)-composite oxide (strontium titanate). Wherein, on vacuum condition, taking thermal treatment to the said substrate to strip with laser the magnesia ceramics material and depositing the laser plasma on the substrate to obtain magnesia thin membrane; monitoring the depositing process till forming said nano line. The product has special properties on optical, electric, magnetism, chemistry.
Description
Technical field
The present invention relates to the microelectronic material field, particularly be applied to the preparation method of nano wire in oxide compound (magnesium oxide)-composite oxides (strontium titanate) hetero epitaxy and surface period structure thereof.
Background technology
Nano wire, nano belt are the novel accurate one-dimentional structure materials of a class, have caused the extensive attention of people on level in research level and the application.This structure has demonstrated superior electricity, optics, mechanics and thermal property, and range of application has covered chemical biosensor, field-effect transistor, function ceramics, opto-electronic device and logical integrated circuit.
On the basis that material character is deeply understood, reasonably design and control this one-dimentional structure, created condition for further preparing new nano structural material and device.Usually, the growth of one-dimensional structural requirement is controlled at nanoscale with the bidimensional of material, and makes the third dimension extend to macro-scale.With respect to the restriction of growth zero dimension and two-dirnentional structure, this requirement makes that control structurally is difficult more.
For two kinds of material systems that have than Macrolattice mismatch, film is easy to adopt layer to combine the mode of (being called " Stranski-Krastanov " pattern) with the island to grow.The strain that accumulates in the two-dimentional soakage layer of initial growth can discharge by the variation that film surface appearance just rises and falls, and does not need by producing misfit dislocation.The unstable of the surface topography that this strain causes makes the shape of three-dimensional island produce anisotropy or is elongated along a certain direction.This is because the diffusion length of adatom is less, so the atomic migration between island and the island can ignore, and sedimentary atom only is adsorbed on the island of nearest neighbour.After the area on island surpasses a threshold value, because the acting in conjunction of surface energy and strain energy will make the growth symmetry on island destroyed, and to the extended transfer of shapes.This changing us into and construct nano wire a new approach is provided in shape.
In the preparation of semiconductor nanowires, this method is at CoSi
2/ Si (100) and (In Ga) has obtained preliminary confirmation in the epitaxial structure of As/GaAs (100).We adopt deposition of magnesium film on strontium titanate (001) monocrystal chip, utilize both caused huge interfacial stresses of lattice mismatch of 8%, utilize the mode of laser molecular beam epitaxy in experiment, to realize the preparation of nanowire in oxide compound (magnesium oxide)-composite oxides (strontium titanate) hetero epitaxy first.Since the anisotropy that sedimentary magnesium oxide spreads at strontium titanate (001) monocrystal chip, and make magnesium oxide present orderly surface period structure at substrate surface, form the nano wire of proper alignment.
Summary of the invention
Technical problem to be solved by this invention is, magnesia nanometer line epitaxial growth and surface period structure preparation method thereof on a kind of strontium titanate (001) monocrystal chip are provided, and the material for preparing has superior electricity, optics, mechanics and thermal property.
The technical scheme that the present invention solve the technical problem employing is that the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip is characterized in that, may further comprise the steps: 1) magnesia ceramics target and strontium titanate monocrystal chip are placed vacuum environment; 2) strontium titanate monocrystal chip is heat-treated; 3) laser lift-off magnesia ceramics target, the laser-(produced)plasma of generation is deposited on the strontium titanate monocrystal chip, makes magnesia film; 4) monitoring deposition process after forming the magnesia nanometer line of orderly surface period structure on the substrate of strontium titanate, stops deposition.
Because when magnesia film thickness reaches 10~14 , the nano wire periodic structure occurs usually, when 12 , effect is best.So described step 4) also can for: measure magnesia film thickness, when thickness reaches 10~14 (preferred value 12 ), stop deposition.Perhaps, by deposition process being made the refletcion high-energy electron diffraction in-situ observation, can observe the diffraction image when the nano wire periodic structure occurring, therefore, described step 4) also can be: deposition process is made the refletcion high-energy electron diffraction in-situ observation, observe diffraction pattern and become point-like by striated, when diffraction pattern again by point-like when striated changes, stop the deposition.Magnesia ceramics target in the described step 1 is a purity greater than 99.9% magnesium oxide polycrystalline ceramics target.
Further, described step 2) be: heating strontium titanate monocrystal chip to 700 ℃, the hold-time is 0.5~2 hour.Preferred value is 2 hours.The depositing temperature of described step 3) is 400~600 ℃, and preferred value is 500 ℃.
Further, described step 1) is: diameter 50mm, thickness 5mm, purity are placed 1.6 * 10 greater than 99.9% magnesium oxide polycrystalline ceramics target and the 001 single-crystal strontium titanate substrate that is orientated
-4The Pa vacuum environment, adjusting target-substrate distance is 50mm; Described step 2) be: heated substrate makes the substrate preheating temperature reach 700 ℃, 2 hours time;
Described step 3) is: under 500 ℃ of temperature, focus on the magnesium oxide polycrystalline ceramics target with laser beam, pulse laser is peeled off magnesium oxide polycrystalline ceramics target, and the laser-(produced)plasma of generation is deposited on the single-crystal strontium titanate substrate, thereby makes magnesia film;
Described step 4) is: control forms the required depositing time of magnesia nanometer line of orderly surface period structure; When depositing time reaches 300s, stop deposition.
Magnesia nanometer line periodic structure of the present invention appears under the situation that thickness is 10~14 , therefore, by observation high energy electron diffraction image, when periodic structure occurring, when thickness satisfies this and requires,
The invention has the beneficial effects as follows that the present invention has prepared the magnesium oxide nanowire with periodic arrangement by the mode of laser molecular beam epitaxy first on single-crystal strontium titanate (001) monocrystal chip.By refletcion high-energy electron diffraction film surface is carried out in-situ observation, control forms the required depositing time of magnesia nanometer line of orderly surface period structure.The magnesia nanometer line with preface surface period structure that the present invention makes is with special light, electricity, magnetic, the voltinism matter that this functional materials of magnesium oxide is embodied be different from bulk in the scope of nanoscale.The magnesia nanometer line with preface surface period structure that the present invention makes also can be as the substrate material of ferroelectric, the superconduction of subsequent growth, semiconductor-quantum-point or quantum wire.
The selected material system of the present invention is single-crystal strontium titanate (001) substrate and magnesia film, both have 8% than the Macrolattice mismatch degree.This bigger lattice mismatch makes film growth be easy to adopt the form of layer island combination and island growth to discharge strain.This provides valuable clue for material system how effectively to choose the preparation nano wire.Magnesia nanometer line of the present invention is because live width is reduced to nanoscale, can strengthen its quantum effect, thereby cause the improvement of various character, produce superior electricity, optics, mechanics and thermal property, for having adopted chemical biosensor of the present invention, field-effect transistor, function ceramics, opto-electronic device and logical integrated circuit, accordingly, performance all obtains very large lifting.
The present invention is further illustrated below in conjunction with the drawings and specific embodiments.
Description of drawings
Fig. 1: the present invention is used to prepare the structural representation of the laser molecular beam epitaxy system of the magnesia nanometer line with orderly surperficial periodic structure.
1-target platform; 2-KrF excimer laser; The lens of 3-laser focusing; 4-heating resistor stove; 5-growth room; 6-refletcion high-energy electron diffraction (RHEED); 7-ccd video camera; 8-microprocessor system; 9-substrate box.
Fig. 2: refletcion high-energy electron diffraction (RHEED) pattern of ccd video camera record.(a) be single-crystal strontium titanate (001) substrate diffractogram after heat treated; Diffractogram during (b) for magnesium oxide deposition 50s; Diffractogram during (c) for magnesium oxide deposition 100s; Diffractogram during (d) for magnesium oxide deposition 300s; Diffractogram during (e) for magnesium oxide deposition 600s.(a) acceptance of the bid ding white ware line is used to write down the spacing variation of diffraction fringe along [100] crystal orientation of strontium titanate (001) substrate.
Fig. 3: the strain that is changed the magnesium oxide relaxation of deriving by the magnesia film diffraction fringe spacing of Fig. 2 (a) acceptance of the bid ding white ware line record concerns that over time X-coordinate is the time, unit: second; Ordinate zou is the strain of relaxation.Sedimentation rate is 0.04 /s.
Fig. 4: the surface topography map of the atomic force microscope of magnesia film (AFM).(a) be that the atomic force microscope of 10 μ m * 10 μ m is overlooked shape appearance figure; (b) be of the variation of film surface height relief along substrate [100] crystal orientation; (c) be the atomic force microscope 3-D view of 5 μ m * 5 μ m.
Embodiment
The magnesia nanometer line with orderly surperficial periodic structure that the present invention is prepared is to utilize laser molecular beam epitaxy technology (L-MBE), on strontium titanate (001) monocrystal chip, ablates and peels off the magnesia ceramics target, makes under high vacuum condition.
The present invention be used to prepare the magnesia nanometer line with orderly surperficial periodic structure laser molecular beam epitaxy system (L-MBE) structural representation as shown in Figure 1.
Concrete, preparation method's step of the present invention is:
(1) selection of magnesia ceramics target: high-purity magnesium oxide polycrystalline ceramics target (more than 99.9%), Ф 50mm * 5mm;
(2) selection of substrate material: select single-crystal strontium titanate (001) substrate for use, substrate is placed on the substrate box 9;
(3) the magnesia ceramics target is placed on the target platform 1, the substrate box is placed on the heating resistor stove 4, the distance of adjusting target and substrate is 50mm (50-100mm within the plasma plume brightness effective radius, the distance of target and substrate should less than this radius);
(4) with vacuum pump growth room 5 is vacuumized and reach 1.6 * 10
-4Pa;
(5) open original position refletcion high-energy electron diffraction (RHEED) 6, the refletcion high-energy electron diffraction pattern is observed by ccd video camera 7, and carries out data acquisition and processing (DAP) with computer 8;
(6) substrate thermal treatment:, make the substrate preheating temperature reach 700 ℃, heat treatment time 2 hours with heating resistor stove 4 heated substrate boxes 9;
(7) film deposition temperature: adjust heating resistor stove 4 electric currents, make depositing temperature reach 500 ℃ of setting;
(8) the starting impulse laser apparatus 2, and pulse laser beam is focused on laser beam on the magnesium oxide polycrystalline ceramics target by condenser lens 3.Pulse laser is peeled off magnesium oxide polycrystalline ceramics target, and the laser-(produced)plasma of generation is deposited on single-crystal strontium titanate (001) substrate, thereby makes magnesia film;
(9) by refletcion high-energy electron diffraction film surface is carried out in-situ observation, form the magnesia nanometer line of orderly surface period structure after, stop the deposition.Can judge whether to form the magnesia nanometer line of orderly surface period structure by observation high energy electron diffraction pattern.
Step (9) also can realize by the control depositing time.Because sedimentation velocity by the power and the frequency decision of laser, has been determined the power and the frequency of laser, can extrapolate required time according to thickness.
Because the magnesia nanometer line with orderly surperficial periodic structure is formed at the magnesia film deposit thickness when being 10~14 , therefore, observation high energy electron diffraction pattern, it in fact also is the variation of observation thickness, it is considered herein that observation high energy electron diffraction pattern also is a kind of mode of measuring thickness.Another kind of mode is owing to sedimentation velocity can be thought at the uniform velocity, can also control deposit thickness by the control depositing time.Therefore no matter, it is considered herein that, be the observation diffraction pattern, still calculates depositing time, and its purpose all is the control deposit thickness.
The electron accelerating voltage of the original position refletcion high-energy electron diffraction (RHEED) in the above-mentioned steps (5) is 20KV, and heater current is 40 μ A, and the grazing angle of electron beam and substrate is 1-3 °;
Said pulsed laser is that the wavelength of selecting for use German LAMBDAPHYSIC company to produce is 248nm in the above-mentioned steps (8), and pulse width is 30ns, and energy density is 2J/cm
2The KrF excimer laser.The pulse-repetition that deposit film is selected for use is 1Hz, and corresponding film deposition rate is 0.04 /s.
The testing tool that the above magnesia nanometer line with orderly surperficial periodic structure that makes carries out structural analysis is as follows:
The film microstructure analytical instrument: atomic force microscope (AFM), model are SPA-300HV, SEIKO.
Below in conjunction with magnesia film refletcion high-energy electron diffraction (RHEED) in-situ observation result and film microstructure analytical results are further specified useful result of the present invention:
Fig. 2: refletcion high-energy electron diffraction in the magnesia film deposition process (RHEED) in-situ observation result.Fig. 2 (a) is single-crystal strontium titanate (001) the substrate diffractogram after heat treated, and sharp-pointed diffraction fringe shape shows the substrate surface of atomic-level flatness.Diffractogram when Fig. 2 (b) deposits 50s for magnesium oxide, the striped of intrinsic magnesia film have begun to occur, and shape of stripes shows that magnesia film is in smooth two-dimentional soakage layer.The diffractogram of Fig. 2 (c) during for magnesium oxide deposition 100s, extended diffraction fringe begins to diffraction spot excessive, illustrate that film is just combining (" Stranski-Krastanov " pattern) with layer at this moment with the island mode grows, and surface roughening begins.Diffractogram when Fig. 2 (d) deposits 300s for magnesium oxide, film island growth pattern that the diffraction spot table is seized with terror, film surface reaches the most coarse degree.Diffractogram when Fig. 2 (e) deposits 600s for magnesium oxide, diffraction pattern are striated (the striated system of this moment is gradually changed by point-like and forms), illustrate that film becomes flat surface again by uneven surface.
Fig. 2 (a) acceptance of the bid ding white ware line is along [100] crystal orientation of strontium titanate (001) substrate, the spacing variation that is used to write down diffraction fringe.By the conversion of the positive space and reciprocal space, the strain that can obtain relaxation in the magnesium oxide deposition process concerns over time, as shown in Figure 3.Show that from Fig. 3 when depositing time 300s, the strain of relaxation enters saturated mode; Corresponding diagram 2 (d), this moment, the form of film island growth was the most obvious.And after the 300s, film can not be again form by island growth discharge strain, but make the film surface smoothing by producing misfit dislocation.So near 300s, should be that film surface rises and falls a most tangible stage.
Stopped laser near 300 seconds, Fig. 4 has shown the surface topography map of the atomic force microscope (AFM) of film this moment.Fig. 4 (a) overlooks shape appearance figure for atomic force microscope, this figure show magnesia nanometer line straight along substrate of strontium titanate [100] crystal orientation periodic arrangement, nanowire width (being the cycle) is about 1~1.3 micron, and every nano wire can reach macroscopical magnitude of millimeter on length.Fig. 4 (b) is the variation of film surface height relief along substrate [100] crystal orientation, and this figure shows that nano wire has the peak-to-valley height value of 5 nanometers.Fig. 4 (c) is the 3-D view of film, has further shown the periodic structure that magnesia film is orderly.
Claims (9)
1, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip is characterized in that, may further comprise the steps:
1) magnesia ceramics target and strontium titanate monocrystal chip are placed vacuum environment;
2) strontium titanate monocrystal chip is heat-treated;
3) laser lift-off magnesia ceramics target, the laser-(produced)plasma of generation is deposited on the strontium titanate monocrystal chip, makes magnesia film;
4) monitoring deposition process after forming the magnesia nanometer line of orderly surface period structure on the substrate of strontium titanate, stops deposition.
2, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, described step 4) is: measure magnesia film thickness, when thickness reaches 10~14 , stop deposition.
3, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1, it is characterized in that, described step 4) is: deposition process is made the refletcion high-energy electron diffraction in-situ observation, observe diffraction pattern and become point-like by striated, when diffraction pattern again by point-like when striated changes, stop the deposition.
4, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, the magnesia ceramics target in the described step 1 is a purity greater than 99.9% magnesium oxide polycrystalline ceramics target.
5, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, described step 2) be: heating strontium titanate monocrystal chip to 700 ℃ kept 0.5~2 hour.
6, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, the depositing temperature of described step 3) is 400~600 ℃.
7, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, the depositing temperature of described step 3) is 500 ℃.
8, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that, described step 4) is: measure magnesia film thickness, when thickness reaches 12 , stop deposition.
9, the method for magnesia nanometer line epitaxial growth from strontium titanate monocrystal chip as claimed in claim 1 is characterized in that,
Described step 1) is: diameter 50mm, thickness 5mm, purity are placed 1.6 * 10 greater than 99.9% magnesium oxide polycrystalline ceramics target and the 001 single-crystal strontium titanate substrate that is orientated
-4The Pa vacuum environment, adjusting target-substrate distance is 50mm;
Described step 2) be: heated substrate makes the substrate preheating temperature reach 700 ℃, 2 hours time;
Described step 3) is: under 500 ℃ of temperature, focus on the magnesium oxide polycrystalline ceramics target with laser beam, pulse laser is peeled off magnesium oxide polycrystalline ceramics target, the laser-(produced)plasma that produces is deposited on the single-crystal strontium titanate substrate, thereby make magnesia film, described optical maser wavelength is 248nm, and pulse width is 30ns, and energy density is 2J/cm
2
Described step 4) is: control forms the required depositing time of magnesia nanometer line of orderly surface period structure; When depositing time reaches 300s, stop deposition.
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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CN106124575A (en) * | 2016-08-08 | 2016-11-16 | 苏州科技大学 | A kind of NO2sensor and preparation method thereof |
CN114242335A (en) * | 2021-12-31 | 2022-03-25 | 苏州新材料研究所有限公司 | Production process for kilometre-level IBAD-MgO long strip |
-
2005
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN106124575A (en) * | 2016-08-08 | 2016-11-16 | 苏州科技大学 | A kind of NO2sensor and preparation method thereof |
CN106124575B (en) * | 2016-08-08 | 2019-12-24 | 苏州科技大学 | NO (nitric oxide)2Sensor and preparation method thereof |
CN114242335A (en) * | 2021-12-31 | 2022-03-25 | 苏州新材料研究所有限公司 | Production process for kilometre-level IBAD-MgO long strip |
CN114242335B (en) * | 2021-12-31 | 2023-12-05 | 苏州新材料研究所有限公司 | Production process for kilometer-level IBAD-MgO long belt |
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