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1.
In this paper, we report on the pulsed laser deposition of epitaxial (0002) oriented Zn1−x
Mg
x
O thin films onto (0001) sapphire substrate in O2 ambient at different deposition temperatures. Pulsed laser deposited Zn1−x
Mg
x
O films showed (0002) oriented hexagonal wurtzite structure up to 34% of Mg concentration. The bandgap of Zn1−x
Mg
x
O thin films is successfully tuned from 3.3 to 4.2 eV by adjusting the Mg concentration x=0.0 to x=0.34. Pulsed laser deposited Zn1−x
Mg
x
O thin films were characterized by XRD, AFM, SEM, PL and UV–VIS spectrometer. We have also studied the effect of deposition
temperature on to the structure, surface morphology and optical properties of Zn1−x
Mg
x
O thin films. 相似文献
2.
G. Epurescu R. Birjega A. C. Galca 《Applied Physics A: Materials Science & Processing》2011,104(3):889-893
Thin films of Mg
x
Zn1−x
O and Mg
x
Zn1−x
O doped with nitrogen were deposited by Radio Frequency plasma beam assisted Pulsed Laser Deposition (RF-PLD) in oxygen or
oxygen-nitrogen discharge with different nitrogen/oxygen ratios. A Nd:YAG laser working at a wavelength of 266 nm, having
a 10 Hz repetition rate was used for the depositions. The energy density of the incident beam was 3 J/cm2 and the RF power was set to 100 W for all the samples. X-ray Diffraction (XRD) and Spectroscopic Ellipsometry (SE) were employed
to investigate the samples. The degree of crystallinity is fount to decrease with increasing the Mg concentration, while the
solubility of Mg in ZnO increases by 30% in the N-doped Mg
x
Zn1−x
O thin films grown by RF-PLD. Segregation of MgO phase at a Mg concentration of 30% for Mg
x
Zn1−x
O thin film is detected both by XRD and SE. The band gap of the samples increases from 3.37 up to 3.57 eV with increasing
the Mg concentration and the nitrogen/oxygen ratio for each Mg concentration. A dependence of the dielectric function (refractive
index) on both stoichiometry and degree of crystalinity is also found, the refractive index having values between 1.7 and
2 in visible spectral range. 相似文献
3.
S. Heitsch G. Benndorf G. Zimmermann C. Schulz D. Spemann H. Hochmuth H. Schmidt T. Nobis M. Lorenz M. Grundmann 《Applied Physics A: Materials Science & Processing》2007,88(1):99-104
MgZnO thin films, MgZnO/ZnO heterostructures (HS) and double heterostructures (DHS) have been prepared on a-plane sapphire
substrates by means of pulsed laser deposition (PLD). A linear blueshift of the MgZnO emission with increasing Mg content
is observed in photoluminescence spectroscopy (PL) at 2 K. Cathodoluminescence measurements verify the spatial homogeneity
of the emission properties of the MgZnO films. The film roughness is evaluated from atomic force microscopy scans. In MgZnO/ZnO
HS the ZnO grows on all appearing MgZnO facets. PL investigations of such PLD-grown heterostructures show the high optical
quality of thin ZnO films (d≤100 nm) grown on MgZnO. Capping those structures with a thin MgZnO layer further improves their
luminescence intensity and enhances the emission of free-exciton luminescence from the ZnO layers. MgZnO/ZnO/MgZnO DHS with
nominal ZnO layer thicknesses of dnom≤6 nm show a clear intensification of the ZnO PL. Temperature dependent PL and transmission measurements between 4.4 and 300 K
prove the dominating emission to be due to the recombination of excitons localized in the ZnO. At 2 K, due to confinement
effects, their emission energy is blueshifted up to 51 meV compared to free excitons in bulk ZnO.
PACS 81.15.Fg; 78.66.Hf; 68.37.Ps 相似文献
4.
N. Rajeswari Yogamalar A. Chandra Bose 《Applied Physics A: Materials Science & Processing》2011,103(1):33-42
Nanopowders of pure and lithium-doped semiconducting ZnO (Zn1−x
Li
x
O, where x= 0, 0.01, 0.03, 0.06, 0.09 and 0.15 in atomic percent (at.%)) are prepared by PEG-assisted low-temperature hydrothermal method.
The average crystallite size is calculated using Debye–Scherrer formula and corrected for strain-induced broadening by Williamson–Hall
(W–H) plot. The peak shift in XRD and the lattice constant of ZnO as a function of unit cell composition are predicted by
Vegard’s law. The evolution of ZnO nanostructures from rod-shaped to particle nature is observed from TEM images and the influence
of dopant on the morphology is investigated. The optical absorption measurement marks an indication that the incorporation
of lithium ion into the lattice of ZnO widens the optical band gap energy from ∼2.60 to ∼3.20 eV. The near band edge (NBE)
emission peak centered at ∼3.10 eV is considered to be the dominant emission peak in the PL spectra. Blue emission peak is
not observed in doped ZnO, thus promoting defect-free nanoparticles. The Burstein–Moss shift serves as a qualitative tool
to analyze the widening of the optical band gap and to study the shape of the NBE luminescence in doped ZnO nanopowders. FT-IR
spectra are used to identify the strong metal–oxide (Zn–O) interaction. 相似文献
5.
M. C. Kao H. Z. Chen S. L. Young 《Applied Physics A: Materials Science & Processing》2010,98(3):595-599
The preferred (002) orientation zinc oxide (ZnO) nanocrystalline thin films have been deposited on FTO-coated glass substrates
by sol–gel spin-coating technology and rapid thermal annealing for use in dye-sensitized solar cells (DSSC). The effects of
preannealing temperature (100 and 300°C) on the microstructure, morphology and optical properties of ZnO thin films were studied.
The ZnO thin films were characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM) and Brunauer–Emmett–Teller
(BET) analysis. The photoelectric performance of DSSC was studied by I–V curve and the incident photon-to-current conversion efficiency (IPCE), respectively. From the results, the intensities of
(002) peaks of ZnO thin films increases with increasing preannealing temperature from 100°C to 300°C. The increase in pore
size and surface area of ZnO films crystallized at the increased preannealing temperature contributed to the improvement on
the absorption of N3 dye onto the films, the short-circuit photocurrent (J
sc) and open-circuit voltage (V
oc) of DSSC. The higher efficiency (η) of 2.5% with J
sc and V
oc of 8.2 mA/cm2 and 0.64 V, respectively, was obtained by the ZnO film preannealed at 300°C. 相似文献
6.
Structural, optical and electrical properties of cadmium zinc oxide films for light emitting devices
B.K. Sonawane Vrushali Shelke M.P. Bhole D.S. Patil 《Journal of Physics and Chemistry of Solids》2011,72(12):1442-1446
Structural, optical and electrical properties of CdyZn1-yO (y=0–0.1) ternary alloy thin films have been investigated for the films prepared using the spin coating method on the glass substrate. XRD pattern confirmed the nano-size polycrystalline hexagonal wurtzite structure for all the samples. The size of nano-crystals was found to be varied in between 21 and 30 nm. Optical band gap calculated from the absorption coefficient signifies the shift in direct band gap from 3.2 to 2.97 eV with cadmium composition. Through EDAX spectrum, it was confirmed that Cadmium was successfully incorporated into ZnO. SEM studies make clear that even after Cadmium incorporation, the surface morphology of the films remained smooth. The current–voltage characteristics obtained from semiconductor characterization system reveals that resistance of the films was found to be decreased with the increase in cadmium composition. Our investigations lead to the applicability of CdZnO as an active layer in CdZnO/ZnO heterostructure for light emitting devices. 相似文献
7.
CdxZn(1−x)S (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) thin films were deposited by the chemical spray pyrolysis technique using a less used combination of chemicals. Depositions were done at 573 K on cleaned glass substrates. The composition, surface morphology and structural properties of deposited films were studied using EDAX, SEM and X-ray diffraction technique. XRD studies reveal that all the films are crystalline with hexagonal (wurtzite) structure and inclusion of Cd into the structure of ZnS improved the crystallinity of the films. The value of lattice constant ‘a’ and ‘c’ have been observed to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm, respectively. The band gap of the thin films varied from 3.32 to 2.41 eV as composition varied from x = 0.0–1.0. It was observed that presence of small amount of cadmium results in marked changes in the optical band gap of ZnS. 相似文献
8.
为适应宽光谱高效率硅基薄膜太阳电池的应用需求,本文尝试采用直流磁控溅射技术在553 K衬底温度下生长氢化Mg和Ga共掺杂ZnO(HMGZO)透明导电氧化物(TCO)薄膜.通过对薄膜微观结构、表面形貌、电学以及光学性能的测试和分析,详细地研究了氢气(H2)流量(0—16.0 sccm)对HMGZO薄膜结晶特性及光电性能的影响.实验结果表明:生长获得的HMGZO薄膜均为六角纤锌矿结构的多晶薄膜,择优取向为(002)晶面生长方向.薄膜的生长速率随着氢气流量的增加呈现逐渐减小趋势,主要归因于溅射产额的减小.适当的氢气引入会引起晶粒尺寸的增加.随着氢气流量由0增加至4.0 sccm,ZnO薄膜电阻率从177?·cm急剧减小至7.2×10-3?·cm,主要是由于H施主的引入显著地增加了载流子浓度;然而进一步增加氢气流量(4.0—16.0 sccm)造成电阻率的轻微增加,主要归因于载流子浓度的减小以及过多氢杂质引入造成杂质散射的增加.所有生长获得的HMGZO薄膜平均光学透过率在波长λ~320—1100 nm范围内可达87%以上.由于Mg的作用及Burstein-Moss效应的影响造成了带隙展宽,带隙变化范围~3.49—3.70 eV,其中最大光学带隙Eg可达~3.70 eV. 相似文献
9.
O. de Melo S. Larramendi L. Martínez A. Climent?Font R. Sanz I. Mínguez?Bacho A. Asenjo M. Jaafar M. Vázquez M. Hernández-Vélez 《Applied Physics A: Materials Science & Processing》2010,99(3):657-664
(Co, Zn)O compound has been obtained by a non-expensive synthesis route. ZnTe thin films were obtained by isothermal close
space sublimation on the Co thin layer previously sputtered on silicon substrates. After the annealing process in humid ambient
cobalt atoms diffusion and Zn oxidation were obtained besides partial Te evaporation. The detailed characterization of the
samples by using XRD, RBS, AFM, XPS, VSM and MFM techniques point to the formation of room temperature ferromagnetic Co
x
Zn(1−x)O phase (x<0.15). This ferromagnetic behavior is mainly attributed to Co atoms substituting Zn atoms in the ZnO network. 相似文献
10.
1 (LO) mode peak at 579 cm-1, indicating oxygen deficiency in the films. Significant dependence of the electrical property for the films on substrate
temperature was shown. The I–V relation of the films exhibited non-ohmic behavior. Whereas the films deposited above 500 °C
showed a metal-like property, at a lower substrate temperature semiconducting thin films were achieved. The (001)-oriented
LiNbO3/ZnO heterostructure was successfully prepared on quartz fused and (001) sapphire plates.
Received: 6 April 1998/Accepted: 26 May 1998 相似文献
11.
The optical and structural properties of mixed ZnO/MgO particles prepared by solution techniques are investigated by the cathodoluminescence and electron microscopy techniques. The samples annealed at 400–1000 °C show well crystalline wurtzite structure of the ZnO (MgZnO) particles with the size in range of 10–100 nm. Annealing at high temperatures (>700 °C) leads to Mg diffusion in ZnO and MgxZn1−xO alloy formation. The blue shifts of the near-band-edge emission as a result of the alloy band gap widening and quantum confinement effect for the small size particles are demonstrated. 相似文献
12.
Y. G. Zhang H. Y. He B. C. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(3):395-400
We theoretically investigate the stabilities and electronic structures of MgZnO nanowires
with different compositions of Mg. It is found that with increasing composition of Mg, wurzite MgZnO
nanowires become less stable, and cubic MgZnO nanowires are energetically favored.
The phase transition from wurzite to cubic structure occurs, when the composition of Mg in the Mg
x
Zn1-
x
O
nanowire reaches about 0.65. Furthermore, our calculations
show that the band gaps can be effectively modulated by composition of Mg for
either wurzite or cubic nanowires. This is reflected in the calculated absorption
spectra, where the absorption edges shift with variation of the compositions of Mg. 相似文献
13.
Wang P. Li J. Lang P. L. Li S. L. Chu H. F. Xie T. Y. Zheng D. N. 《Applied Physics A: Materials Science & Processing》2011,102(2):449-455
High quality La2/3Ca1/3MnO4(LCMO) thin films have been deposited on silicon-on-insulator (SOI) substrates only buffered by yt tria-stabilized zirconia
(YSZ) by using the pulsed laser deposition (PLD) technique. The results obtained from X-ray diffraction (XRD), reflection
high energy electron diffraction (RHEED), scanning electron microscopy (SEM) and magnetization investigations indicate that
the LCMO films are highly oriented both in-plane and out-of-plane. The Curie temperature T
c is close to 260 K and the insulator–metal (I–M) transition appears around 220 K. The conducting mechanism at low temperatures
is dominated by the electron–magnon scattering. A tensile stress from the film–substrate lattice mismatch results in magnetic
‘easy axes’ in the film plane and the magnetic anisotropy energy increases with cooling. A maximum magnetoresistance (MR) is observed near 190 K, with the external magnetic field either parallel or vertical to the LCMO film plane. Moreover, the
large intrinsic high-field magnetoresistance (HFMR) and the very small extrinsic low-field magnetoresistance (LFMR) again
reveal that the LCMO films on SOI substrates are highly oriented thin films of good crystallinity. 相似文献
14.
Polycrystalline Pb1−x
Sr
x
(Fe0.012Ti0.988)O3 (0.2≤x≤0.4) (PSFT) thin films have been grown on fused quartz substrates by metallo-organic decomposition technique. The grown films
were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), source meter and UV–Vis–NIR spectrophotometer
to determine the structural, microstructural, dc resistivity and optical properties. The XRD pattern confirmed that the PSFT
films has distorted tetragonal single phase, which close to cubic at higher Sr concentration. AFM analysis revealed that the
grains size reduces with increasing Sr concentration and their average values lies in the range of 26–9 nm. The higher values
of dc resistivity of PSFT nano grains indicate that the transmission of light occurs within these grains up to short wavelength.
The refractive index and the extinction coefficient were determined from the optical transmission spectrum in the wavelength
range of 200–1100 nm and compared with that theoretically calculated, when fitted to a single oscillator model. The values
of optical band gap were determined from Tauc’s extrapolation fitting and suggests that the transformation of electrons during
transmission of light through local states within Fermi gap. 相似文献
15.
Jiahua Min Xiaoyan Liang Bin Wang Linjun Wang Yue Zhao Weimin Shi Yiben Xia 《Journal of nanoparticle research》2011,13(10):5171-5176
Field ionization gas sensors based on ZnO nanorods (50–300 nm in diameter, and 3–8 μm in length) with and without a buffer
layer were fabricated, and the influence of the orientation of nano-ZnO on the ionization response of devices was discussed,
including the sensitivity and dynamic response of the ZnO nanorods with preferential orientation. The results indicated that
ZnO nanorods as sensor anode could dramatically decrease the breakdown voltage. The XRD and SEM images illustrated that nano-ZnO
with a ZnO buffer layer displayed high c-axis orientation, which helps to significantly reduce the breakdown voltage. Device A based on ZnO nanorods with a ZnO buffer
layer could distinguish toluene and acetone. The dynamic responses of device A to the NO
x
compounds presented the sensitivity of 0.045 ± 0.007 ppm/pA and the response speed within 17–40 s, and indicated a linear
relationship between NO
x
concentration and current response at low NO
x
concentrations. In addition, the dynamic responses to benzene, isopropyl alcohol, ethanol, and methanol reveals that the
device has higher sensitivity to gas with larger static polarizability and lower ionization energy. 相似文献
16.
利用脉冲激光沉积技术,通过改变沉积过程中的氧气压力,在蓝宝石(0001)基片上制备了一系列ZnMgO合金.通过X射线衍射、反射和透射光谱以及室温和变温荧光光谱,对薄膜的结构和光学性能进行了系统地表征,分析了工作气压对ZnMgO合金薄膜的结晶质量及光学特性的影响.研究结果表明:随着沉积环境中氧气压力的增大,ZnMgO薄膜的结晶质量下降,富氧环境下,与蓝宝石晶格平行的ZnO晶粒的出现是导致薄膜结晶质量下降的主要原因;相对于本征ZnO,不同氧气环境下沉积的ZnMgO薄膜的紫外荧光峰均出现了不同程度的蓝移.随着工
关键词:
ZnO
Mg掺杂
脉冲激光沉积
薄膜生长
光学特性 相似文献
17.
《Current Applied Physics》2015,15(9):1010-1014
A polycrystalline MgZnO/ZnO bi-layer was deposited by using a RF co-magnetron sputtering method and the MgZnO/ZnO bi-layer TFTs were fabricated on the thermally oxidized silicon substrate. The performances with varying the thickness of ZnO layer were investigated. In this result, the MgZnO/ZnO bi-layer TFTs which the content of Mg is about 2.5 at % have shown the enhancement characteristics of high mobility (6.77–7.56 cm2 V−1 s−1) and low sub-threshold swing (0.57–0.69 V decade−1) compare of the ZnO single layer TFT (μFE = 5.38 cm2 V−1 s−1; S.S. = 0.86 V decade−1). Moreover, in the results of the positive bias stress, the ΔVon shift (4.8 V) of MgZnO/ZnO bi-layer is the 2 V lower than ZnO single layer TFT (ΔVon = 6.1 V). It reveals that the stability of the MgZnO/ZnO bi-layer TFT enhanced compared to that of the ZnO single layer TFT. 相似文献
18.
H. Kim A. Cepler C. Cetina D. Knies M. S. Osofsky R. C. Y. Auyeung A. Piqué 《Applied Physics A: Materials Science & Processing》2008,93(3):593-598
Present p-type ZnO films tend to exhibit high resistivity and low carrier concentration, and they revert to their natural n-type state
within days after deposition. One approach to grow higher quality p-type ZnO is by codoping the ZnO during growth. This article describes recent results from the growth and characterization
of Zr–N codoped p-type ZnO thin films by pulsed laser deposition (PLD) on (0001) sapphire substrates. For this work, both N-doped and Zr–N
codoped p-type ZnO films were grown for comparison purposes at substrate temperatures ranging between 400 to 700 °C and N2O background pressures between 10−5 to 10−2 Torr. The carrier type and conduction were found to be very sensitive to substrate temperature and N2O deposition pressure. P-type conduction was observed for films grown at pressures between 10−3 to 10−2 Torr. The Zr–N codoped ZnO films grown at 550 °C in 1×10−3 Torr of N2O show p-type conduction behavior with a very low resistivity of 0.89 Ω-cm, a carrier concentration of 5.0×1018 cm−3, and a Hall mobility of 1.4 cm2 V−1 s−1. The structure, morphology and optical properties were also evaluated for both N-doped and Zr–N codoped ZnO films. 相似文献
19.
I. Vasiliu M. Gartner M. Anastasescu L. Todan L. Predoana M. Elisa C. Grigorescu C. Negrila C. Logofatu M. Enculescu A. Moldovan G. Pavelescu M. Zaharescu 《Optical and Quantum Electronics》2007,39(4-6):511-521
We intend to prepare periodic multilayered structures for photonic applications. With this goal we have performed a study
of some characteristics of SiO
x
-P2O5 films deposited by the sol–gel method on glass and ITO (InSnO
x
)-coated glass. The as prepared films were annealed to different temperatures (150 and 200°C). The chemical composition of
the samples was determined by X-ray Photoelectron Spectroscopy (XPS). The XPS results revealed the presence of P in the as-deposited
films. The structural an optical properties were examined by Fourier Transform Infrared Spectroscopy (FTIR), Spectroellipsometry
(SE) and UV Transmission Spectroscopy. IR spectra of the deposited films attest the interaction of an amorphous SiO2 with the H3PO4 used as a P-precursor. Refractive indices for individual SiO
x
-P2O5 determined from SE measurements show a densification of the layer structure with the increasing temperature in the thermal
treatment. The UV transmission spectra revealed a lower transmission for the sol-gel SiO
x
-P2O5 films as compared to ITO/glass substrate. AFM images proved the densification of the films with annealing in agreement with
the ellipsometric results.
The work was originally presented at “Physics of Photonic Crystals and Metamaterials (PPCM)” Workshop, Brussels, 12–15 June,
2006. 相似文献
20.
L. B. Duan X. R. Zhao J. M. Liu T. Wang G. H. Rao 《Applied Physics A: Materials Science & Processing》2010,99(3):679-683
Zn1−x
Cr
x
O (0≤x≤0.15) nanoparticles were synthesized by an auto-combustion method and characterized by x-ray diffraction and Raman scattering
techniques. The solubility limit for Cr in ZnO was determined as x≈0.03. Room-temperature ferromagnetism (RT-FM) was observed in lightly Cr-doped ZnO nanoparticles with x=0.01 and 0.02. Raman scattering spectra of the lightly Cr-doped and Co-doped ZnO were studied and compared. The enhancement
of both the magnetization and the intensity of Raman scattering peak associated with donor defects (Zni and/or VO) and carriers indicates that light Cr doping in ZnO could be an effective way to achieve pronounced RT-FM and the ferromagnetism
is closely related to the dopant-donor hybridization besides the ferromagnetic Cr–O–Cr superexchange interactions. 相似文献