High Resolution Electron Microscopy Studies of Nickel Oxide Thin Films Deposited on Ito
TF10:
Thin Films for Electronics and Optics
Posters
TF10.1.P
THE STRUCTURE AND CERTAIN PROPERTIES OF Pb(Ti,Zr)O3 THIN FILMS
A.F. Andreeva, A.M. Kasumov, S.V. Utkin
The Institute for Problems of Materials Science of the National Academy of Sciences
Krzhyzhanovsky St. 3,. Kiev - 142, 03680, Ukraine
e-mail:
thin Pb(Ti,Zr)03 (PZT) films are perspective for the using in optical and acoustic electronics as an infrared radiation detectors, a ferroelectrics memory elements, and so on. wide application of PZT films is retarded by the unperfectnesses of their obtaining methods. The cVD methods (sol-gel, spincoat) release the reactive gases I2, Cl2 and others that is practically incompatible with the other microelectronics processes. The laser evaporation disturbs the PZT films stoichiometry. The HF-sputtering of PZT fouls the condensates with a residual gases because of a small deposition rate. A sputtering of several targets gives the irreproducible composition and properties of PZT layers. Diffusion in oxide films of Ti, Pb and Zr has small rates and requires the high temperatures (over 1000C). thus a research for effective methods to obtain PZT films is the actual problem.
In this work a possibility was investigated to make PZT films through the reaction synthesis of solid Pb-Ti-Zr solutions. The films were obtained on a polished SiO2, NaCl, and the pyroceram at 300 - 800 K. the deposition rate was 10 - 15 nm/s, the films thickness 0.05 - 0.8 m. the MDM (metal-dielectric-metal) structures were obtained with the bottom electrode of the low-resistance SnO2 or Fe and with the In point top electrode.
The PZT films obtained at 500 K were amorphous. With growth of condensation temperature to 600 K films crystallization was occurred in the perovskite structure. For PZT films with the thickness 0.8 m. on Fe underlayers the calculated value of the dielectric constant was of several thousands order.
the advantages of reaction synthesis method for PZT films obtaining are a low deposition temperatures and the allowance to perform all technology in one cycle including a modification of the composition and properties of the ferroelectric by a doping.
TF10.2.P
The Perspectives of the Application of the Rare-Earth metalS Oxides Thin films in Optics and Electronics
A.F. Andreeva
The Institute for Problems of Materials Science of the National Academy of Sciences
Krzhyzhanovsky St. 3,. Kiev - 142, 03680, Ukraine
e-mail:
The structure and properties of the rare-earth metals oxides (REMO) thin films were investigated. The films were obtained by a reaction synthesis - an evaporation of the metal in O2 atmosphere. It was shown that the REMO films are perspective for using as:
The masking layers with a high wear resistance and the low density of defects (density of defects of size 1.5 m was 0.06 cm 2) for the transparent photolithography templates. It is possible to produce photolithography templates of planar construction due to the phase transformations in masking layer of the praseodymium oxide. It turns out in this case that all glass surface of substrate is covered by protecting REMO layer consisting of transparent and non-transparent sites according to the topology. Owing to this fact occurs the additional increase of templates wear resistance by preventing the knocking out of the glass surface and the ability appears to use mask layers many times, saving additionally resources and work expenses.
Optical REmO coatings have high transparency in wide spectral diapason 0.19 15 m, refractive index is 1.92.2, light dispersion loss of laser REMO-SiO2 mirrors < 0.005%, the threshold of the stationary radiation strength to concentrated light flux during 120 s was greater than 2.5 kW/cm2.
The REMO films are perspective for the using in capacitors and in multilevel integrated circuits. They have high electric resistivity 1015 1016 Ohmcm, low dielectric loss 110-4; high puncture strength 107 -108 V/cm.
The based on REMO high temperature and a heat flux sensors have the following characteristics: the flux measured range is 108 W/cm2, the time constant is <0.1 s, the temperature coefficient of electric resistance at 200C is 0.06 - 0.08 0C-1.
TF10.3.P
SILICON OXYNITRIDE FOR SILICON INTEGRATED OPTICS
O.P.Agnihotri1*, Hee Chul Lee1, B.S.Sahu2, and Pankaj Srivastava2
1 Department of Electrical Engineering and Computer Science, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
2 Semiconductor Engineering Laboratory, I. I. T., New Delhi, India
Growth of low refractive index (~1.5) and hydrogen free silicon oxynitride by a low temperature deposition process could play a significant role in the fabrication of integrated optical components on silicon substrates. We have used a photosensitized chemical vapor deposition process to grow silicon oxynitride at a substrate temperature 0f 350C which could be used for the fabrication of low loss optical waveguide on silicon substrates. We used a gaseous mixture of SiH4 (2% in Ar),NH3 and N2O under 253.7 nm UV radiation. The oxynitride composition was varied by changing N2O:(N2O+NH3) ratio while keeping N2O+NH3 and SiH4 flow rates constant. The refractive index could be tailored from 1.46 to 1.95. The optical energy gap increases from 4.8 eV to 5.7 eV as the flow rate ratio varies from 0 to 0.25. At the flow rate ratio of 0.25,the resistivity of silicon oxynitride was 3.5x1014 ohm-cm and the refractive index was 1.51. The midgap interface state density of silicon oxynitride/Si MIS devices was 8.5x1010 cm-2 eV-1. The infrared absorption showed no evidence of Si-H and N-H bonds. The oxynitride grown in this work could therefore be used as a low loss optical waveguide material for silicon integrated optics [1,2].
- K.Wörhoff, A.Driessen, P.V.Lamback, L.T.H.Hielderink, P.W.C.Linders and Th.J.A.Popma: Sensors and Actuars 74 (1999) 9.
2. O.P.Agnihotri, S.C.Jain, J.Poortmans, J.Szlufcik, G.Beaucarne, J.Nijs and R.Mertens: Semicond.Sci. Technol. 15 (2000) R29.
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TF10.4.P
DIELECTRIC CHARACTERISTICS OF RF-MAGNETRON SPUTTERED YTTRIUM OXIDE THIN FILMS DEPOSITED ON PLASMA-ETCHED SILICON SUBSTRATES
J.J. Araiza1, M. Aguilar-Frutis2, C. Falcony3,*
1Unidad Académica de Física, U.A.Z.. Av. Preparatoria
# 301, C.P. 98060, Zacatecas, México.
2CICATA-IPN, Miguel Hidalgo 11500, México, DF México,
3CINVESTAV-IPN, Apdo. Postal 14-740, 07000, México, DF México
High quality yttrium oxide thin films were deposited on Si(100) substrates by rf-magnetron sputtering. The films were deposited at low temperatures; from room temperature, and up to 300º C. The characteristics of the films were studied as a function of the different etching times of the silicon substrates. Films free from –OH or water related bonds are obtained with high refractive indexes, depending on the experimental conditions. X-ray diffraction measurements of the films show that they are mainly polycristalline, presenting the cubic and/or the monoclinic phases of the yttrium oxide. The incorporation of these films into Metal-Oxide-Semiconductor structures show that they can stand electric fields close to 5 MV/cm, and with dielectric constants higher than 11. The surface state density of the MOS structures, determined at midgap of the semiconductor, was in the range of 1011 cm-2eV-1. Atomic force microscopy and energy dispersive spectroscopy measurements are also presented.
The financial support by CONACyT-Mexico, under grant: G37858-E is acknowledged
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*Corresponding author: C. Falcony
Tel. (+) 52 55 5747 3703
Fax (+) 52 55 5747 7096
e-mail address:
TF10.5.P
OPTICAL, STRUCTURAL AND ELECTRICAL CHARACTERISTICS OF RF-MAGNETRON SPUTTERED ALUMINUM OXYNITRIDE THIN FILMS DEPOSITED ON SILICON SUBSTRATES
J.J. Araiza1, M. Aguilar-Frutis2,*, C. Falcony3, M. Jergel3,4, M. Garcia2,5
1Unidad Académica de Física, U. A. Z.. Av. Preparatoria
# 301, C.P. 98060, Zacatecas, México.
2CICATA-IPN, Miguel Hidalgo 11500, México, DF México,
3CINVESTAV-IPN, Apdo. Postal 14-740, 07000, México, DF México
4Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia
5IIM-UNAM, Coyoacan 04510, México, DF México
The optical, structural and electrical characteristics of rf-magnetron sputtered aluminum oxynitride thin films are reported. The films were deposited at room temperature and up to 300º C without any further thermal treatments. The characteristics of the films were studied as a function of the substrate temperature during deposition and the flow ratio of nitrogen to argon in the sputtering chamber. Films free from –OH or water related bonds were obtained with a high refractive index, depending on the experimental conditions during deposition. X-ray diffraction measurements of the films show that they are mostly amorphous. The incorporation of these films into Metal-Oxide-Semiconductor structures show that they can withstand electric fields up to 5 MV/cm, without observing destructive dielectric breakdown. The effect of a plasma etching process, carried out on the substrates previous to deposition of the films, is also discussed.
The financial support by CONACyT-Mexico, under grants: J34225-U and G37858-E is acknowledged. The partial support from CGPI-IPN grant # 20010281 is also acknowledged.
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*Corresponding author: M. Aguilar-Frutis
Tel. (+) 52 55 5729 6000 ext. 67738
Fax (+) 52 55 5557 5103
e-mail address:
TF10.6.P
LASER-STIMULATED TRANSFORMATIONS IN AMORPHOUS Si/Ge AND AsxSe1-x/TeySe1-y - TYPE MULTILAYERS
Beke D.L1, Csik A.1, Kikineshi A.1,2, Langer G.1, Malyovanik M.2, Shipljak M.2
1Debrecen University, Debrecen, Hungary
2Uzhgorod National University, Uzhgorod, Ukraine
Recent development of thin film technology has made it possible to fabricate high-quality multilayer structures (MLS) from different amorphous semiconductors [1,2]. Some properties of these structures are similar to the compositionally modulated superlattices with modulation periods L=5-20 nm [2], therefore the size-dependent effects in optical and electrical characteristics can be investigated and related to the initial structure, interface mixing. We have extended our investigations of laser-beam-induced interdiffusion in a-Se/As2S3 amorphous MLS to the number of AsxSe1-x/TeySe1-y-type and Si/Ge structures, which were less sensitive to the direct photo-stimulated transformations but exhibited considerable changes of optical transmission in the given spectral regions, DC- and photo-conductivity due to the thermal annealing by focused laser beam.
60-300 nm thick Si/Ge structures were prepared by ciclic magnetron sputtering, while amorphous AsxSe1-x/TeySe1-y MLS with 0.1 x 0.5, 0.1 y 0.4 and total thickness d up to 1-2 m were fabricated by ciclic thermal evaporation of corresponding initial glasses in vacuum. All structures were deposited onto transparent sapphire or silica-glass substrata, therefore optical transmission measurements of MLS were performed mostly in the wavelegth region of absorption edge of the narrow-band component (i.e. Ge, TeySe1-y). Well-definied blue-shift of absorption edge was observed in all MLS, which depended on the modulation period and can be additionally changed by constant or pulsed laser beam illumination at 0.51, 0.53, 0.63, 0.69 m. Thus optical transmission of the MLS for the given small-intensity read-out laser beam can be effectively changed. The effects of laser-induced enlightenment correlate well with the changes of the refractive index, reflectivity and electrical conductivity in all investigated MLS in the 100-350 K temperature range. The mechanism of the observed effects was explained in the framework of the interdiffusion model, which takes into account the laser-beam heating of the MLS.
Besides fundamental interest these results are applicable for producing certain solid-state solutions, mixtures of amorphous materials and for spatial patterning, direct writing of thin film optical elements.
1. Nesheva D., Arsova D., Levi Z. Phil.Mag. B69, 205 (1994)
2. Csik A., Malyovanik M., Dorogovich J., Kikineshi A., Beke D.L., Szabo I.A., Langer G. Journ. of Optoelectronics and Advanced Materials, 3, 33 (2001)
TF10.7.P
Reflectance of thin thermal oxide layer grown on c-Si substrate - statistical evaluation
Róbert Brunner1, Juraj Dillinger2, Emil Pinčík1.
1 Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovakia
2 Department of Physics, Slovak University of Technology, Faculty of Mechanical Engineering, Námestie slobody 17, 812 31 Bratislava, Slovakia
We present the enhanced reflectance measurements of optical and geometrical parameters of thin films - i.e. films, the thickness of which is less than wavelength of the light. These parameters are calculated as a coefficients of best fit of the dispersion curve of the reflectance data. The enhancement is based on statistical test, which enables to estimate confidence interval of the measured parameters. Both reflectance spectroscopy and standard ellipsometry investigations were performed and the obtained results were compared.
The reflectance of the samples was measured for normally incident light using fiber-optics spectrometer. Optical properties of layered structure were described by standard mathematical model, based on 2x2 overall transfer matrix formalism. Tabulated empirical values of the complex refractive index of crystalline silicon substrate were used in these calculations. Parameters of oxide layer, were evaluated in fitting process of measured reflectance spectra. Simple phenomenological model of material dispersion of thin film, based on first order polynomial expansion, was used. Subsequently, the statistical test utilizing the resampling procedure was applied to the measured data set and the confidence intervals for estimated parameters of the structure were determined. The main advantage of the real data based numerical simulation is, that none a priori information, which should regard data error distribution function, is required.
The reconstruction of material parameters using reflectance data is the inverse task, which is often badly conditioned. In consequence, the possibility to estimate the errors of measurement of the structure parameters and the ability to judge the stability of the calculated results without any preliminary assumption is very useful and can be unavoidable in most cases.
TF10.8.P
PULSED LASER DEPOSITION OF Cd1-xMnxTe THIN FILMS
A.P. Caricato, E. D’Anna, M. Fernández, G. Leggieri, A. Luches, E. Mero, M. Martino.
INFM and University of Lecce, Department of Physics, 73100 Lecce, Italy
The semimagnetic semiconductor Cd1-xMnxTe is a very interesting material due to its various properties connected with the presence of the magnetic ion (Mn). In particular the energy gap and the lattice constant can be tuned varying the Mn content. Moreover the spin-exchange interaction between this ion and the conduction band electrons is responsible of different phenomena like, for example, a giant Faraday rotation near the fundamental absorption edge. This property is of interest in the design of fiber optic magnetic field sensors.
Pulsed laser ablation is a well-suited technique for the deposition of thin films of such compound materials since, unlike the evaporation processes, it preserves the stoichiometry of the target. Cd1-xMnxTe thin films (0.6–0.7 m) were deposited by laser ablation of targets with different Mn content (x=0.05, 0.36, 0.43 and 0.50). Ablation was performed with a XeCl laser (=308 nm, =30 ns) at a fluence of 6 J/cm2. Films were deposited on sapphire substrates placed at 40 mm from the target and heated at 250 °C. Energy dispersive spectroscopy and optical transmission measurements in the 200 – 3500 nm range were performed on the deposited films. From these characterizations it was possible to evaluate the band-gap energy and the composition of the films. The film stoichiometry resulted in quite good agreement with the one of their relative targets, although the deposited samples presented a lower Cd incorporation. Scanning electron microscopy inspection showed that the surface morphology is good for films with low magnetic ion (Mn) concentration (x=0.05). The surface quality of the films deteriorates with increasing Mn concentration, due to the presence of sub-micron droplets. From photoluminescence spectroscopy only the peak at 2.0 eV, associated to the Mn2+ 6A1(6S) 4T2(4G) transition, was detected in samples with x 0.36.
TF10.9.P
STRUCTURAL AND PHOTOLUMINESCENT PROPERTIES OF TERBIUM AND EUROPIUM DOPED ZINC ALUMINATE FILMS SYNTHESIZED BY PYROSOL TECHNIQUE.
M. García-Hipólitoa, C. D. Hernández-Péreza, A. Corona-Ocampoa, R. Martíneza, O. Alvarez-Fragosoa, E. Martíneza and C. Falconyb,c.
a Instituto de Investigaciones en Materiales, UNAM, A.P. 70-360 Coyoacán 04510 México, D. F.
b Departamento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, México D F. 07000.
Dense ZnAl2O4 coatings have been synthesized by ultrasonic spray pyrolysis deposition process using aluminum chloride and zinc acetate. The preparation, structural and luminescent properties of zinc aluminate films doped with Tb3+ and Eu3+ ions are presented. Different substrate temperatures and doping concentrations in the start spraying solution were studied. The elemental composition was measured by Energy Dispersive Spectroscopy (EDS). X-ray diffraction analyses demonstrated that the films were single-phase cubic corresponding to spinel. The excitation and emission spectra of Tb3+ and Eu3+ ions were measured. Concentration quenching of the photoluminescence was observed. In addition, the surface morphology of the films was investigated.
This contribution will be presented by: Manuel García-Hipólito..
TF10.10.P
ELECTRICAL CONDUCTIVITY AND DYNAMICS OF ELECTRO-FORMING IN Al-SiOx-Al THIN FILM SANDWICH STRUCTURES
R.D. Gould and M.G. Lopez
Thin Films Laboratory, Department of Physics, School of Chemistry and Physics,
Keele University, Keele, Staffs. ST5 5BG, U.K.
Many insulating thin film materials, including silicon oxide (SiOx), exhibit a high-field electrical conduction process on the application of relatively low voltages. The dominant high-field conduction process in SiOx appears to be the Poole-Frenkel effect, in which the high field leads to a lowering of the potential barrier between donor-like centres and the bottom of the conduction band. Such behaviour is usually indicated by a linear dependence of log J on V1/2, where J is the current density and V is the applied voltage. Since this type of process is bulk limited, it normally occurs irrespective of the type of metal contacts.
Identical structures frequently show an effect known as electroforming, in which following the application of several volts under moderate vacuum conditions, the conductance increases by several orders of magnitude and shows other characteristic features such as voltage-controlled differential negative resistance (VCNR) and elecron emission. In contrast with the Poole-Frenkel effect, electroforming is very sensitive to the type of electrodes used, with those having noble metals such as gold electroforming easily, while others, including aluminium, electroform with difficulty. Recent work has established that in samples having gold electrodes the value of the Poole-Frenkel field-lowering coefficient generally increases with the number of DC voltage cycles reqiired before electroforming, frequently attaining a value of up to twice the theoretical value. The enhanced values were associated with the establishment of non-uniform electric field region during voltage cycling, which was considered a necessary condition for the onset of electroforming.
In the present work aluminium electrodes were used in order to explore the characteristics of a contrasting system. Electroforming occurred in some samples, but with a maximum current value of less than 1 mA, considerably lower than with gold electrodes. Poole-Frenkel conductivity was observed in the initial voltage cycles, with a value of typically 4.5 10-5 eV m1/2 V-1/2, moderately exceeding the theoretical value. Electroforming normally took place after several voltage cycles, but was not permanent, with a reversion to Poole-Frenkel conduction during some cycles. As for the case with gold electrodes, the value of increased in the first few cycles, but after further voltage cycling the behaviour became less stable with varying values of . This behaviour can be understood in terms of a filamentary conduction model where the stability of samples with aluminium electrodes is inferior to those with gold electrodes as a consequence of the lower melting point.
Corresponding author R.D. Gould. Telephone 00-44-(0)1782 5833316; Fax 00-44-(0)1782 712378; E-mail R.D. . Address: Department of Physics, School of Chemistry and Physics, Keele University, Keele, Staffs. ST5 5BG, U.K.