Preparing aluminum-doped zinc oxide transparent conducting films of a kind of high mobility and preparation method thereof
Technical field
The present invention relates to field of photovoltaic materials, be specifically related to preparing aluminum-doped zinc oxide transparent conducting films of a kind of high mobility and preparation method thereof.
Background technology
Transparent conductive oxide (transparentconductiveoxide, be called for short TCO) film be one roughly the same time there is high visible light transmissivity and the film of conductivity, be widely used in Low emissivity window, gas sensor, flat-panel monitor, thin-film transistor, the field such as light-emitting diode and solar cell.Most of TCO thin film is based on tin ash (SnO
2), indium oxide (In
2o
3), zinc oxide (ZnO) and compound thereof, formed by different physics and chemistry deposition techniques.Wherein, aluminium-doped zinc oxide (AluminiumdopedZnicoxide, be called for short AZO) transparent conductive film with low, nontoxic, the high radiation resistance of its cost, in hydrogen plasma, the advantage people such as comparatively stable receives publicity, and is widely used as the front electrode of thin-film solar cells.
As a kind of front electrode, AZO transparent conductive film is supposed to have higher conductivity and lower absorptivity.Because high carrier concentration can cause charge carrier, increase light absorption, the particularly light absorption of near-infrared section.So, it may be necessary and improve mobility and keep the way of moderate carrier concentration to realize this purpose simultaneously, become the key of exploitation for the high-quality AZO film of film photovoltaic.
Current preparation AZO transparent conductive film comparative maturity and what extensively adopt is magnetron sputtering technique, adopt glass substrate, the AZO film mobility of preparation is generally between 1 ~ 30cm more
2v
-1s
-1.In theory when AZO transparent conductive film carrier concentration is higher than 5 × 10
20cm
-3time, mobility can not higher than 40cm
2v
-1s
-1(Resistivityofpolycrystallinezincoxidefilms:currentstatus andphysicallimit, JournalofPhysicsD:AppliedPhysics, calendar year 2001 the 34th volume 3097-3108).Publication number is that CN101985740 Chinese invention patent application discloses a kind of method improving AZO nesa coating mobility, and the program AZO transparent conductive film of Grown by Magnetron Sputtering is put into the annealing in process that annealing furnace carries out vacuum or introduce certain atmosphere (inertia, reducing atmosphere).Although the method can realize low temperature fast filming, and batch short annealing obtains the nesa coating of high conductivity, and when process annealing process to the raising limitation of AZO transparent conductive film mobility, final mobility is no more than 20cm
2v
-1s
-1; And although the high temperature anneal can bring optical transmittance to promote, film conductivity will be caused again significantly to reduce, also namely be difficult to ensure high electric conductivity and optical transmittance simultaneously.The people such as Wimmer (ImprovingtheelectricalandopticalpropertiesofDC-sputtered ZnO:Albythermalpostdepositiontreatments, ThinSolidFilms, 520th volume 4203-4207 page in 2012) adopt plasma reinforced chemical vapour deposition (PECVD) method to grow the thick amorphous silicon overlay film of one deck 50nm by the AZO surface deposited at direct current sputtering, and then 500 DEG C are annealed 6 hours, by carrier mobility from 27cm
2v
-1s
-1bring up to 48cm
2v
-1s
-1.Adopt and use the same method, the people such as Warzecha (HighmobilityannealingofTransparentConductiveOxides, IOPConf.Series:MaterialsScienceandEngineering, 34th volume 012004 in 2012) by 650 DEG C of annealing 24 hours, by mobility from 40cm
2v
-1s
-1bring up to 72cm
2v
-1s
-1.Although this method substantially increases the mobility of AZO transparent conductive film, complex process, heat treatment time is long, and load is large, and cost is high.The people such as Kang (EffectsofITOprecursorthicknessontransparentconductiveAld opedZnOfilmforsolarcellapplications, SolarEnergyMaterials & SolarCells, 2011,95,138-141 page) by depositing tin indium oxide (ITO) precursor layer of different-thickness, by the mobility of AZO film from 5.4cm
2v
-1s
-1bring up to 23.6cm
2v
-1s
-1, resistivity is from 1.99 × 10
-3Ω cm is reduced to 3.63 × 10
-4Ω cm, visible ray mean transmissivity brings up to 90.0% from 82.1%, and near infrared light mean transmissivity brings up to 89.6% from 88.1%.Although this method makes film be improved significantly in optical transmittance and conductivity, owing to have employed ITO, cost is high, and mobility is still on the low side in addition.
As can be seen from the above document about preparing high mobility AZO transparent conductive film, although mobility can be improved by annealing or increasing the methods such as precursor layer, there is the AZO transparent conductive film mobility obtained not too high (generally lower than 40cm
2v
-1s
-1), or treatment process length consuming time, power consumption is large, high in cost of production shortcoming.And develop the high mobility that preparation is simple, the processing time is short, cost is low and (be greater than 40cm
2v
-1s
-1) method of AZO transparent conductive film is still very necessary.
Summary of the invention
Not enough for solving existing AZO transparent conductive film, the invention provides preparing aluminum-doped zinc oxide transparent conducting films of a kind of high mobility and preparation method thereof.
A kind of preparing aluminum-doped zinc oxide transparent conducting films of high mobility, comprise glass substrate, AZO Seed Layer and AZO body layer from bottom to up successively, described AZO Seed Layer is 50 ~ 200nm, described AZO body layer thickness is 800 ~ 1300nm, and the mobility of described preparing aluminum-doped zinc oxide transparent conducting films is 40-60cm
2v
-1s
-1, resistivity is 2 × 10
-4~ 5 × 10
-4mean transmissivity in Ω cm, 400 ~ 1200nm wave-length coverage is greater than 80%.
In the present invention, AZO Seed Layer can promote grain growth by AZO body layer, improves crystalline quality, reduces crystal defect, reduce the r.m.s. roughness of film surface, thus reducing from the scattering of defect with surface in carrier transport process, raising mobility, reduces resistivity.In described AZO Seed Layer, the mass ratio of aluminium oxide and zinc oxide is higher than the mass ratio of aluminium oxide and zinc oxide in AZO body layer.
In described AZO Seed Layer, the mass ratio of aluminium oxide and zinc oxide is 0.008 ~ 0.04:1.In described AZO body layer, the mass ratio of aluminium oxide and zinc oxide is 0.001 ~ 0.01:1.
Due to alumina content low time, the crystallinity of AZO Seed Layer is poor, upper layer main body layer film crystallinity is caused not to be effectively increased, in order to ensure Seed Layer crystallinity, thus effectively improve the crystallinity of AZO body layer, therefore make the mass ratio of aluminium oxide in AZO Seed Layer and zinc oxide a little more than AZO body layer in the present invention.And aluminium (Al) doping content lower time, the ionized impurities scattering caused by doped with Al is low, to obtain higher mobility, therefore, making the mass ratio of aluminium oxide and zinc oxide in AZO Seed Layer be the mass ratio of aluminium oxide and zinc oxide in 0.008 ~ 0.04:1, AZO body layer is 0.001 ~ 0.01:1.
As preferably, in AZO Seed Layer, the mass ratio of aluminium oxide and zinc oxide is the mass ratio of aluminium oxide and zinc oxide in 0.008:1, AZO body layer is 0.005:1.
Crystallite dimension is the bigger the better, but by preparation process technology limit, the crystallite dimension of described AZO body layer is 40 ~ 60nm.
In described AZO film, the preferred orientation of crystal is (002).
Except there is impure ion scattering mechanism, scattering mechanism, particularly crystal boundary scattering mechanism that some cause due to such as crystallographic defect and crystal boundary is also there is in the AZO film of polycrystalline.The ZnO film obtaining perfectly (002) preferred orientation is also the very crucial factor improving Electrical performance.Therefore, it may be necessary very much and control the ZnO crystal that sedimentary condition obtains initial stage of growth perfection (002) orientation, so obtain have height preferred orientation, crystalline quality with the AZO transparent conductive film of electric property excellence.
A preparation method for the preparing aluminum-doped zinc oxide transparent conducting films of high mobility, comprises the steps:
(1) direct current magnetron sputtering process sputtering AZO ceramic target is adopted, deposition obtains the thick AZO Seed Layer of 50 ~ 200nm on a glass substrate, sputtering condition is: sputter gas is the gaseous mixture of high purity oxygen gas and high-purity argon gas, the volume ratio of oxygen and argon gas is 0 ~ 1:1, and sputtering pressure is 0.2 ~ 0.8Pa; Substrate temperature is 200 ~ 400 DEG C;
(2) direct current magnetron sputtering process sputtering AZO ceramic target is adopted, AZO Seed Layer deposits the thick AZO body layer of 800 ~ 1300nm, form preparing aluminum-doped zinc oxide transparent conducting films, sputtering condition is: sputter gas is high-purity argon, sputtering pressure is 0.2 ~ 0.8Pa, and substrate temperature is 200 ~ 400 DEG C;
(3) preparing aluminum-doped zinc oxide transparent conducting films is carried out short annealing under oxygen-free environment, annealing temperature is 400 ~ 600 DEG C, and annealing time is 2 ~ 10min.
In the present invention, AZO Seed Layer and AZO body layer all adopt magnetically controlled DC sputtering, and by changing sputtering pressure, sputter rate reaches 20 ~ 40nm/min, and sputter rate is high, and the RTA time is short, is convenient to quick mass disposal sample.
In described Seed Layer AZO ceramic target, the mass ratio of aluminium oxide and zinc oxide is higher than the mass ratio of aluminium oxide and zinc oxide in Seed Layer AZO ceramic target.
In described Seed Layer AZO ceramic target, the mass ratio of aluminium oxide and zinc oxide is 0.008 ~ 0.04:1.
In described body layer AZO ceramic target, the mass ratio of aluminium oxide and zinc oxide is 0.001 ~ 0.01:1.
The alumina doped AZO of high concentration is adopted to do Seed Layer in preparing aluminum-doped zinc oxide transparent conducting films of high mobility of the present invention and preparation method thereof, technique is heat-treated simple in the employing quick thermal annealing method short time, consuming time short, power consumption is few, cost is low, and applicable AZO transparent conductive film prepares process in enormous quantities; And preparing aluminum-doped zinc oxide transparent conducting films mobility of the present invention 40 ~ 60cm
2v
-1s
-1, resistivity is 2 × 10
-4~ 5 × 10
-4in Ω cm, 400 ~ 1200nm wave-length coverage, transmitance is higher than 80%, and this film is applicable to the front electrode being applied to thin-film solar cells, contributes to the photoelectric conversion efficiency improving solar cell.
Accompanying drawing explanation
Fig. 1 is the AZO transparent conductive film structural representation of embodiment 1 ~ 4;
Fig. 2 (a) is the XRD collection of illustrative plates of the AZO transparent conductive film of deposited in embodiment 2;
Fig. 3 (a) is the AZO transparent conductive film AFM picture of deposited in embodiment 2;
The AZO transparent conductive film that Fig. 4 (a) is deposited in embodiment 2 in 300 ~ 2400nm wave-length coverage through spectrum;
Fig. 2 (b) is the XRD collection of illustrative plates of the AZO transparent conductive film after 600 DEG C of annealing in embodiment 2;
Fig. 3 (b) is the AZO transparent conductive film AFM picture after 600 DEG C of annealing in embodiment 2;
Fig. 4 (b) in embodiment 2 600 DEG C annealing after AZO transparent conductive film in 300 ~ 2400nm wave-length coverage through spectrum;
Fig. 2 (c) is the XRD collection of illustrative plates of the AZO transparent conductive film of deposited in comparative example 1;
Fig. 3 (c) is the AZO transparent conductive film AFM picture of deposited in comparative example 1;
The AZO transparent conductive film that Fig. 4 (c) is deposited in comparative example 1 in 300 ~ 2400nm wave-length coverage through spectrum;
Fig. 5 is the AZO transparent conductive film structural representation of comparative example 1.
Embodiment
Below with reference to specific embodiments and the drawings, the present invention is further described.It is glass substrate that various embodiments of the present invention and comparative example all select thickness to be the ultra-clear glasses of 1.85mm.
Embodiment 1
Selecting the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.008:1 is Seed Layer AZO target, magnetically controlled DC sputtering is adopted to obtain the thick AZO Seed Layer of 50nm in a kind of sugar, produced in chao'an county deposition on glass, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 8 minutes, sputter gas is high-purity (purity is greater than 99.999%) argon gas (namely the volume ratio of oxygen and argon gas is 0:1), and gas flow is 30sccm, and operating pressure is 0.4Pa.
And then to select the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.005:1 be body layer AZO target, adopt magnetically controlled DC sputtering to deposit in AZO Seed Layer and obtain the AZO body layer that thickness is 1200nm, namely the AZO transparent conductive film of deposited is obtained, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 50 minutes, sputter gas is high-purity (purity is greater than 99.999%) argon is sputter gas, gas flow is 30sccm, and operating pressure is 0.4Pa.
The AZO nesa coating of deposition is put into annealing furnace, and logical high-purity (purity is greater than 99.999%) argon, anneal 4min at 600 DEG C.
Prepare AZO transparent conductive film structure as shown in Figure 1 by above method, comprise successively from bottom to up: Al in glass substrate 1, AZO Seed Layer 2 and AZO body layer 3, AZO Seed Layer 2
2o
3be Al in 0.008:1, AZO body layer 3 with the mass ratio of ZnO
2o
3the mass ratio right with ZnO is 0.005:1.
The crystal structure of the AZO transparent conductive film of the deposited of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and resistivity is 4.1 × 10
-4Ω cm, mobility is 41.3cm
2v
-1s
-1, carrier concentration is 3.6 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity is 80.2%.
The crystal structure of the AZO transparent conductive film after 600 DEG C of annealing of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and crystallite dimension is 49nm, and resistivity is 3.5 × 10
-4Ω cm, mobility is 51.9cm
2v
-1s
-1, carrier concentration is 3.4 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity is 81.3%.
Embodiment 2
Selecting the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.008:1 is Seed Layer AZO target, adopt magnetically controlled DC sputtering to deposit in ultra-clear glasses and obtain the thick AZO Seed Layer of 130nm, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 8 minutes, sputter gas is the mist of high-purity (purity is greater than 99.999%) argon gas and high-purity (purity is greater than 99.999%) oxygen, the volume ratio of oxygen and argon gas is 1:2, gas flow is 30sccm, and operating pressure is 0.4Pa.
And then to select the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.005:1 be body layer AZO target, adopt magnetically controlled DC sputtering to deposit in AZO Seed Layer and obtain the AZO body layer that thickness is 1230nm, namely the AZO transparent conductive film of deposited is obtained, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 50 minutes, sputter gas is high-purity (purity is greater than 99.999%) argon is sputter gas, gas flow is 30sccm, and operating pressure is 0.4_Pa.
The AZO nesa coating of deposition is put into annealing furnace, and logical high-purity (purity is greater than 99.999%) argon, anneal 4min at 600 DEG C.
Prepare AZO transparent conductive film structure as shown in Figure 1 by above method, comprise successively from bottom to up: Al in glass substrate 1, AZO Seed Layer 2 and AZO body layer 3, AZO Seed Layer 2
2o
3be Al in 0.008:1, AZO body layer 3 with the mass ratio of ZnO
2o
3be 0.005:1 with the mass ratio of ZnO.
The XRD collection of illustrative plates of the AZO transparent conductive film that Fig. 2 (a) is deposited, can find out that the crystal structure of the AZO transparent conductive film of deposited is the hexagonal wurtzite phase structure along (002) orientation, crystallite dimension is 48nm.
The AZO transparent conductive film AFM picture of the deposited that Fig. 3 (a) is the present embodiment, the surface Root Mean Square roughness obtaining the AZO transparent conductive film of the deposited of the present embodiment is 10nm.
The AZO transparent conductive film of the deposited that Fig. 4 (a) is the present embodiment in 300 ~ 2400nm wave-length coverage through spectrum, the mean transmissivity of AZO transparent conductive film (containing glass substrate) in 400 ~ 1200_nm wave-length coverage obtaining the deposited of the present embodiment is 80.7%.
The resistivity that electrical properties test obtains the AZO transparent conductive film of deposited is 4.3 × 10
-4Ω cm, mobility is 45.5cm
2v
-1s
-1, carrier concentration is 3.2 × 10
20cm
-3.
The XRD collection of illustrative plates of the AZO transparent conductive film after 600 DEG C of annealing that Fig. 2 (b) is the present embodiment, can find out that the crystal structure of the AZO transparent conductive film of deposited is the hexagonal wurtzite phase structure along (002) orientation, crystallite dimension is 51nm.
AZO transparent conductive film AFM picture after 600 DEG C of annealing that Fig. 3 (b) is the present embodiment, the surface Root Mean Square roughness obtaining the AZO transparent conductive film of the deposited of the present embodiment is 10_nm.
AZO transparent conductive film after 600 DEG C of annealing that Fig. 4 (b) is the present embodiment in 300 ~ 2400nm wave-length coverage through spectrum, the mean transmissivity of AZO transparent conductive film (containing glass substrate) in 400 ~ 1200nm wave-length coverage obtaining the deposited of the present embodiment is 81.1%.
The resistivity of the AZO transparent conductive film that electrical properties test obtains after 600 DEG C of annealing of the present embodiment is 4.0 × 10
-4Ω cm, mobility is 53.9cm
2v
-1s
-1, carrier concentration is 2.9 × 10
20cm
-3.
Embodiment 3
Selecting the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.008:1 is Seed Layer AZO target, adopt magnetically controlled DC sputtering to deposit in ultra-clear glasses and obtain the thick AZO Seed Layer of 150nm, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 8 minutes, sputter gas is the mist of high-purity (purity is greater than 99.999%) argon gas and high-purity (purity is greater than 99.999%) oxygen, the volume ratio of oxygen and argon gas is 1:9, gas flow is 30sccm, and operating pressure is 0.4Pa.
And then to select the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.005:1 be body layer AZO target, adopt magnetically controlled DC sputtering to deposit in AZO Seed Layer and obtain the AZO body layer that thickness is 1210nm, namely the AZO transparent conductive film of deposited is obtained, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200_W, sputtering time is 50 minutes, sputter gas is high-purity (purity is greater than 99.999%) argon is sputter gas, gas flow is 30sccm, and operating pressure is 0.4Pa.
The AZO nesa coating of deposition is put into annealing furnace, and logical high-purity (purity is greater than 99.999%) argon gas, anneal 10min at 400 DEG C.
Prepare AZO transparent conductive film structure as shown in Figure 1 by above method, comprise successively from bottom to up: Al in glass substrate 1, AZO Seed Layer 2 and AZO body layer 3, AZO Seed Layer 2
2o
3with ZnO) mass ratio is Al in 0.008:1, AZO body layer 3
2o
3be 0.005:1 with ZnO mass ratio.
The crystal structure of the AZO transparent conductive film of the deposited of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and resistivity is 4.5 × 10
-4Ω cm, mobility is 43.9cm
2v
-1s
-1, carrier concentration is 3.0 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity is 80.2%.
The crystal structure of the AZO transparent conductive film after 600 DEG C of annealing of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and crystallite dimension is 50nm, and resistivity is 4.1 × 10
-4Ω cm, mobility is 50.4cm
2v
-1s
-1, carrier concentration is 3.0 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity is 81.7%.
Embodiment 4
Selecting the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.008:1 is Seed Layer AZO target, adopt magnetically controlled DC sputtering to deposit in ultra-clear glasses and obtain the thick AZO Seed Layer of 170nm, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 8 minutes, sputter gas is the mist of high-purity (purity is greater than 99.999%) argon gas and high-purity (purity is greater than 99.999%) oxygen, the volume ratio of oxygen and argon gas is 1:4, gas flow is 30sccm, and operating pressure is 0.4Pa.
Selecting the mass ratio of aluminium oxide and zinc oxide to be the AZO ceramic target of 0.005:1 is body layer AZO target, adopt magnetically controlled DC sputtering to deposit in AZO Seed Layer and obtain the AZO body layer that thickness is 1200nm, namely the AZO transparent conductive film of deposited is obtained, sputtering condition is: substrate temperature is 350 DEG C, sputtering power is 200W, sputtering time is 50 minutes, sputter gas is high-purity (purity is greater than 99.999%) argon is sputter gas, gas flow is 30sccm, and operating pressure is 0.4Pa.
The AZO nesa coating of deposition is put into annealing furnace, and logical high-purity (purity is greater than 99.999%) argon gas, anneal 2min at 600 DEG C.
Prepare AZO transparent conductive film structure as shown in Figure 1 by above method, comprise successively from bottom to up: Al in glass substrate 1, AZO Seed Layer 2 and AZO body layer 3, AZO Seed Layer 2
2o
3with ZnO) mass ratio is Al in 0.008:1, AZO body layer 3
2o
3be 0.005:1 with the mass ratio of ZnO.
The crystal structure of the AZO transparent conductive film of the deposited of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and crystallite dimension is 46nm, and resistivity is 4.4 × 10
-4Ω cm, mobility is 43.1cm
2v
-1s
-1, carrier concentration is 3.1 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity equals 80.4%.
The crystal structure of the AZO transparent conductive film after 600 DEG C of annealing of the present embodiment is the hexagonal wurtzite phase structure along (002) orientation, and crystallite dimension is 50nm, and resistivity is 4.2 × 10
-4Ω cm, mobility is 51.3cm
2v
-1s
-1, carrier concentration is 2.9 × 10
20cm
-3, in 400 ~ 1200nm wave-length coverage, mean transmissivity equals 81.6%.
Comparative example 1
Be sputtering target material by the AZO ceramic target that the mass ratio of aluminium oxide and zinc oxide is 0.005:1, with high-purity (purity is greater than 99.999%) argon gas for sputter gas, adopt magnetically controlled DC sputtering, ultra-clear glasses sputters thickness 1200nm one deck AZO transparent conductive film, namely obtains the AZO transparent conductive film without Seed Layer.Sputtering condition is: sputter gas is high-purity (purity is greater than 99.999%) argon gas, and gas flow is 30sccm, and operating pressure is 0.4Pa, and underlayer temperature is 350 DEG C, and sputtering power is 200_W, and sputtering time is 50 minutes.
AZO transparent conductive film without Seed Layer prepared by above method as shown in Figure 5, specifically comprises, glass substrate 1a and the AZO film 3a be positioned on glass substrate 1a, Al in AZO film
2o
3be 0.005:1 with ZnO mass ratio.
The XRD collection of illustrative plates of the AZO transparent conductive film that Fig. 2 (c) is this comparative example, can find out, this AZO film crystal structure is the hexagonal wurtzite phase structure along (002) orientation, and crystallite dimension is 33nm.
The AFM picture that Fig. 3 (c) is this AZO film, the surface roughness of this AZO film is 21_nm.
Fig. 4 (c) for this AZO film in 300 ~ 2400_nm wave-length coverage through spectrum, can find out that this AZO film equals 80% at the mean transmissivity of visible region.
Obtained by electrical properties test, the resistivity of this AZO film is 7.2 × 10
-4Ω cm, mobility 33.5cm
2v
-1s
-1, carrier concentration is 2.6 × 10
20cm
-3.
Should be understood that, the above-mentioned statement for preferred embodiment in the present invention is comparatively detailed, and therefore can not think the restriction to scope of patent protection of the present invention, scope of patent protection of the present invention should be as the criterion with appending claims.