One-step growth of thin film SnS with large grains using MOCVD

Thin film tin sulphide (SnS) films were produced with grain sizes greater than 1 μm using a one-step metal organic chemical vapour deposition process. Tin–doped indium oxide (ITO) was used as the substrate, having a similar work function to molybdenum typically used as the back contact, but with potential use of its transparency for bifacial illumination. Tetraethyltin and ditertiarybutylsulphide were used as precursors with process temperatures 430–470 °C to promote film growth with large grains. The film stoichiometry was controlled by varying the precursor partial pressure ratios and characterised with energy dispersive X-ray spectroscopy to optimise the SnS composition. X-ray diffraction and Raman spectroscopy were used to determine the phases that were present in the film and revealed that small amounts of ottemannite Sn₂S₃ was present when SnS was deposited on to the ITO using optimised growth parameters. Interaction at the SnS/ITO interface to form Sn₂S₃ was deduced to have resulted for all growth conditions.     

Thermal stability of hafnium silicate dielectric films deposited by a dual source liquid injection MOCVD

The hafnium and silicon precursors, Hf(NMe₂)₄ and Bu^tMe₂SiOH, have been investigated for the MOCVD of high-κ hafnium silicate, (HfO₂)_1–x –(SiO₂) _x films for gate dielectric applications. Control of the silica concentration in the hafnium silicate can be achieved by varying the relative precursor ratios up to a saturation level of 35–40% SiO₂. The thermal stability of the resulting hafnium silicate films in air has been investigated using medium energy ion scattering. Internal oxidation of the underlying silicon substrate is discernable when the films are annealed in dry air for 15 min over the temperature range 800–1000 °C.     

Thermal stability of hafnium silicate dielectric films deposited by a dual source liquid injection MOCVD

The hafnium and silicon precursors, Hf(NMe₂)₄ and Bu^tMe₂SiOH, have been investigated for the MOCVD of high- hafnium silicate, (HfO₂)_1–x –(SiO₂) _x films for gate dielectric applications. Control of the silica concentration in the hafnium silicate can be achieved by varying the relative precursor ratios up to a saturation level of 35–40% SiO₂. The thermal stability of the resulting hafnium silicate films in air has been investigated using medium energy ion scattering. Internal oxidation of the underlying silicon substrate is discernable when the films are annealed in dry air for 15 min over the temperature range 800–1000 °C.     

C、Hf薄膜抑制栅极电子发射的机理研究

利用双离子束溅射和射频磁控溅射技术在Mo基底上分别制备了C膜和Hf膜,并利用化学方法制备了BaO涂层以模拟行波管栅极结构,随后在N2保护下,通过在900～1300K范围内退火,研究样品处于高温工作环境下表面相结构和成分的变化,以此解释了C、Hf薄膜抑制栅极电子发射的工作机理.     

C、Hf薄膜抑制栅极电子发射的机理研究

利用双离子束溅射和射频磁控溅射技术在Mo基底上分别制备了C膜和Hf膜，并利用化学方法制备了BaO涂层以模拟行波管栅极结构．随后在N2保护下．通过在900～1300K范围内退火．研究样品处于高温工作环境下表面相结构和成分的变化．以此解释了C、Hf薄膜抑制栅极电子发射的工作机理。     

Influence of annealing on ZnO thin film grown by plasma-assisted MOCVD

ZnO films were grown on C-plane sapphire substrate by plasma-assisted MOCVD. The films was characterized by XRD, photoluminescence (PL) and the optical transmission spectrum. We found tensile strain in the sample, which had been annealed many times during the growth process, while there is compressive strain in the sample, which was annealed only one time after growth. The PL spectra at room temperature for the sample annealed many times exhibited only one emitting peak at around 380 nm. However, we find Γ₅ and Γ₆ free exciton peaks in the sample annealed only one time after growth. At the same time, the optical transmission indicate that the maximum of the sample's transmission decreases against with the increasing of the c-axis length in ranges from 190 to 900 nm.     

Oriented growth of thin films of samarium oxide by MOCVD

Thin films of Sm₂O₃ have been grown on Si(100) and fused quartz by low-pressure chemical vapour deposition using an adducted β-diketonate precursor. The films on quartz are cubic, with no preferred orientation at lower growth temperatures (∼ 550°C), while they grow with a strong (111) orientation as the temperature is raised (to 625°C). On Si(100), highly oriented films of cubic Sm₂O₃ at 625°C, and a mixture of monoclinic and cubic polymorphs of Sm₂O₃ at higher temperatures, are formed. Films grown on either substrate are very smooth and fine-grained. Infrared spectroscopic study reveals that films grown above 600° C are free of carbon.     

Synthesis of TiO2 thin films using single molecular precursors by MOCVD method for dye-sensitized solar cells application and study on film growth mechanism

For dye-sensitized solar cells application, in this study, we have synthesized TiO₂ thin films at deposition temperature in the range of 300–750 °C by metalorganic chemical vapor deposition (MOCVD) method. Titanium(IV) isopropoxide, {TIP, Ti(OⁱPr)₄} and Bis(dimethylamido)titanium diisopropoxide, {BTDIP, (Me₂N)₂Ti(OⁱPr)₂} were used as single source precursors that contain Ti and O atoms in the same molecule, respectively. Crack-free, highly oriented TiO₂ polycrystalline thin films with anatase phase were deposited on Si(1 0 0) with TIP at temperature as low as 450 °C. XRD and TED data showed that below 500 °C, the TiO₂ thin films were dominantly grown in the [2 1 1] direction on Si(1 0 0), whereas with increasing the deposition temperature to 700 °C, the main film growth direction was changed to [2 0 0]. Above 700 °C, however, rutile phase TiO₂ thin films have only been obtained. In the case of BTDIP, on the other hand, only amorphous film was grown on Si(1 0 0) below 450 °C while a highly oriented anatase TiO₂ film in the [2 0 0] direction was obtained at 500 °C. With further increasing deposition temperatures over 600 °C, the main film growth direction shows a sequential change from rutile [1 0 1] to rutile [4 0 0], indicating a possibility of getting single crystalline TiO₂ film with rutile phase. This means that the precursor together with deposition temperature can be one of important parameters to influence film growth direction, crystallinity as well as crystal structure. To investigate the CVD mechanism of both precursors in detail, temperature dependence of growth rate was also carried out, and we then obtained different activation energy of deposition to be 77.9 and 55.4 kJ/mol for TIP and BTDIP, respectively. Also, we are tested some TiO₂ film synthesized with BTDIP precursor to apply dye-sensitized solar cell.     

Preparation and optical characterization of MOCVD ZnCdInS thin films

The precursor, bis-(morpholinodithiocarbamate-s,s′)-Cd–Zn–In has been prepared and pyrolyzed to obtain ZnCdInS thin films. The results of the compositional studies carried out using RBS and EDXRF were found to be complementary. An optical band gap of 2.53 eV was obtained from both absorbance and PL measurements.     

Modelization of hafnium silicate chemical vapor deposition using tetrakis-diethyl-amino-hafnium and tetrakis-dimethyl-amino-silane

The Chemical Vapor Deposition growth mechanism of a hafnium silicate film deposited by means of the co-flow of two precursors, TDEAH (tetrakis-diethyl-amino-hafnium) and 4DMAS (tetrakis-dimethyl-amino-silane), is characterized. Typical growth kinetics demand that the deposition rate increases and the silicon concentration remain stable with increasing reactor pressure. Though the deposition rate follows the expected growth kinetics, the silicon concentration in the silicate does not and exhibits an abnormal increase with increasing reactor pressure. To understand this atypical behavior the formation of pure HfO₂ from TDEAH and pure SiO_x from 4DMAS is first studied. Experimental results show that whereas the HfO₂ deposition is well behaved and fits a diffusion-based model defined by assuming diffusion of TDEAH through a boundary layer, the deposition of SiO_x with 4DMAS requires Hf-O nucleation sites and self-saturates after a single Si―O monolayer is formed. Based on these observations, a model is developed for hafnium silicate formation. The Atomic Layer Deposition like behavior of 4DMAS decomposition results in a deposition rate and film stoichiometry that are weakly sensitive to the 4DMAS partial pressure, and instead are driven by the TDEAH reaction. Since TDEAH operates within a transport-limited regime, the deposition rate is insensitive to substrate temperature, and is only controlled by the TDEAH partial pressure and the gas phase kinematics, rendering the process robust and easily controllable with excellent reproducibility.     

Synthesis and characterization of hafnium tert-butylacetoacetate as new MOCVD precursor for HfO2 films

A new hafnium β-ketoesterate Hf(tbob)₄ (tbob=tert-butyl-3-oxobutanoate or tert-butylacetoacetate) was obtained by ligand exchange reaction applied to Hf₂(OⁱPr)₈(ⁱPrOH)₂. It was characterized by elemental analysis, FT-IR, ¹H NMR, mass-spectroscopy and TGA. The compound is volatile and it was tested for the growth of HfO₂ films on Si(100) and R-plane sapphire substrates at 600–800 °C by pulsed liquid injection MOCVD. The films were characterized by XRD, XPS and AFM. Stoichiometric amorphous films were obtained on silicon, while those on sapphire were relatively well crystallized (00l) monoclinic. The growth was kinetically limited in all the temperature range studied (600–800°C).     

The growth of thin films of copper chalcogenide films by MOCVD and AACVD using novel single-molecule precursors

Highly oriented crystalline films of copper sulfide and copper selenide have been grown on glass by low-pressure metal-organic chemical vapor deposition (LP-MOCVD) and by aerosol-assisted chemical vapor deposition (AACVD), using the novel air-stable compounds Cu(E₂CNMeⁿHex)₂]* (where E=S,Se). Thin films of non-stoichiometric cubic CuS and CuSe have been deposited in the temperature range 450–500 °C.     

Microstructural and textural characterization in MgO thin film using HRTEM

The microstructural and texture evolution of MgO protective films deposited on Si and glass substrates by ebeam evaporation were investigated. MgO films on both types of substrates consisted of a well developed columnar structure showing <111> texture in the cross sectional view and a triangle shape in the plane view. It was found that there is amorphous MgO between each columnar, which occupies 8-25% in the MgO films. The electron energy loss spectroscopy (EELS) spectrum of amorphous MgO showed features of chemical states and electronic structures different from those of crystalline MgO.     

Boron thin film deposition by using Thermionic Vacuum Arc (TVA) technology

In this paper a new technology for boron thin film deposition is presented. The film in high vacuum conditions is condensing on the sample from the plasma state of the vapor phase of the anode material, generated by a Thermionic Vacuum Arc (TVA). Boron coating is one of the technologies recently considered to be of special interest due to the qualities of boron. The aim of this paper is to present the use of TVA technology for boron coating.     

Atomic layer deposition of SiO2 thin films using tetrakis(ethylamino)silane and ozone

We examined the atomic layer deposition (ALD) of silicon dioxide thin films on a silicon wafer by alternating exposures to tetrakis(ethylamino)silane [Si(NHC2H5)4] and O3. The growth kinetics of silicon oxide films was examined at substrate temperatures ranging from 325 to 514 degrees C. The deposition was governed by a self-limiting surface reaction, and the growth rate at 478 degrees C was saturated at 0.17 nm/cycle for Si(NHC2H5)4 exposures of 2 x 10(6) L (1 L = 10(-6) Torr x s). The films deposited at 365-404 degrees C exhibited a higher deposition rate of 0.20-0.21 nm/cycle. However, they contained impurities, such as carbon and nitrogen, and showed poor film qualities. The concentration of impurities decreased with increasing substrate temperature. It was found that the films deposited in the high-temperature regime (478-514 degrees C) showed excellent physical and electrical properties equivalent to those of LPCVD films.     

NiTi thin film characterization by Rutherford backscattering spectrometry

Nickel and titanium can form alloys showing the shape memory effect when combined in the right stoichiometric proportion (1:1). Recently, such alloys have been produced as thin films by sputtering (RF or DC, with or without magnetron), with a view to making microelectromechanical actuators. Precise control of the characteristic transformation temperature is crucial for obtaining the shape memory effect. This requires analytical tools which can accurately determine the relative composition, and hence the transition temperature. In this paper, Rutherford backscattering spectrometry will be shown to meet the requirements of thin film processing of NiTi shape memory alloys, and to have advantages when compared with other techniques.     

Synthesis and characterization of BN thin films prepared by plasma MOCVD with organoboron precursors

Boron nitride (BN) films have contributed to improvement of tribological parts. For this study, we prepared films using plasma MOCVD with an organoborate precursor and investigated the mechanical properties and structure of BN films. The BN films were formed on specimens of silicon wafers and tungsten carbide (WC) substrates at low temperatures of less than 500 °C. Hardness tests were carried out to evaluate mechanical properties of BN films. The structure of BN films was investigated using XRD, Raman, and FT-IR spectra.     

In situ oxygen conditioning of (001) MgO thin film substrates for film growth studies by electron microscopy

It was found that the in situ treatment of (001) single-crystal films of MgO (prepared by epitaxial growth from the vapor phase) at high temperatures with a jet of oxygen will produce a surface that is almost equivalent, for epitaxial studies, to surfaces with the same orientation prepared by vacuum cleavage of bulk single crystals. The effectiveness of the process is demonstrated by its impact on the epitaxy of silver.     

Formation of secondary iron-sulphur phases during the growth of polycrystalline iron pyrite (FeS2) thin films by MOCVD

Thin films of iron pyrite (FeS₂) have been prepared on glass and glassy carbon substrates by low pressure metal organic chemical vapour deposition (LP-MOCVD) using iron pentacarbonyl (Fe(CO)₅) and di-tert.-butyldisulphide (TBDS) as precursors. The TBDS partial pressure was varied from 1 to 100 Pa for different iron pentacarbonyl partial pressures (0.25, 0.5 and 1 Pa) while all other parameters were maintained constant. It was found that there is a critical TBDS-partial pressure of about 30 Pa for a deposition temperature of 475 °C, where a drastic change in the layer properties occurs. Below this TBDS partial pressure pyrrhotite type phases (Fe_1-xS) will be formed although there is a sulphur precursor excess in the gas phase. If the layers contain pyrrhotite, the electrical properties of the FeS_x-films are changed significantly. The occurrence of the pyrrhotite phases does not depend on the growth rate, hence it is not controlled kinetically. Therefore, the sulphur pressure above the growing pyrite film is the important parameter controlling the solid phase. The present investigation shows that, in order to prepare pyrite thin films of good electronic quality, one has to take care to avoid the secondary sulphur-iron phases even in very small concentrations.