Synthesis, characterization and application of Ni(tta)2.tmeda to MOCVD of nickel oxide thin films

A novel nickel beta-diketonate adduct, Ni(tta)2.tmeda, has been synthesized using 2-thenoyltrifluoroacetone as the beta-diketonate and N,N,N,'N'-tetramethylethylendiamine as the Lewis base. It has been characterized by elemental analyses, IR, 1H NMR, 13C NMR spectroscopy and single-crystal X-ray diffraction studies. Physical and thermal properties of Ni(tta)2.tmeda precursor have been also extensively investigated. Its efficacy as a metal-organic chemical vapour deposition (MOCVD) precursor for the growth of nickel oxide films has been fully tested by applying it to the deposition of NiO films on quartz substrate. NiO thin films have been characterized by X-ray diffraction (XRD), scanning electron microscopy and UV spectroscopy.     

Synthesis and characterisation of zirconium-amido guanidinato complex: a potential precursor for ZrO2 thin films

A new zirconium complex, bis-(ethylmethylamido)-bis-(N,N'-diisopropyl-2-ethylmethylamidoguanidinato)-zirconium(iv) {[(N(i)Pr)(2)C(NEtMe)](2)Zr(NEtMe)(2)}, was synthesised by partial replacement of amide ligands with bidentate guanidinate ligands. The monomeric Zr complex was characterised by (1)H-NMR, (13)C-NMR, EI-MS, elemental analysis, and single crystal X-ray diffraction studies. The thermal properties of the compound was studied by thermogravimetric and differential thermal analysis (TG/DTA). The new Zr compound is thermally stable and can be sublimed quantitatively which renders it promising for thin film growth using vapor deposition techniques like chemical vapor deposition (CVD) and atomic layer deposition (ALD). The use of this complex for CVD of ZrO(2) on Si(100) substrates was attempted in combination with oxygen as the oxidant. Stoichiometric ZrO(2) films with preferred orientation at lower growth temperatures was obtained and the films were almost carbon free. The preliminary electrical characterisation of ZrO(2) films showed encouraging results for possible applications in dielectric oxide structures.     

Guanidinate-stabilized monomeric hafnium amide complexes as promising precursors for MOCVD of HfO2

Novel guanidinato complexes of hafnium [Hf{eta2-(iPrN)2CNR2}2(NR2)2] (R2 = Et2, 1; Et, Me, 2; Me2, 3), synthesized by insertion reactions of N,N'-diisopropylcarbodiimide into the M-N bonds of homologous hafnium amide complexes 1-3 and {[mu2-NC(NMe2)2][NC(NMe2)2]2HfCl}2 (4) using a salt metathesis reaction, are reported. Single-crystal X-ray diffraction analysis revealed that compounds 1-3 were monomers, while compound 4 was found to be a dimer. The observed fluxional behavior of compounds 1-3 was studied in detail using variable-temperature and two-dimensional NMR techniques. The thermal characteristics of compounds 1-3 seem promising for HfO2 thin films by vapor deposition techniques. Metal-organic chemical vapor deposition experiments with compound 2 as the precursor resulted in smooth, uniform, and stoichiometric HfO2 thin films at relatively low deposition temperatures. The basic properties of HfO2 thin films were characterized in some detail.     

MOCVD-derived highly transparent, conductive zinc- and tin-doped indium oxide thin films: precursor synthesis, metastable phase film growth and characterization, and application as anodes in polymer light-emitting diodes

Four diamine adducts of bis(hexafluoroacetylacetonato)zinc [Zn(hfa)(2).(diamine)] can be synthesized in a single-step reaction. Single crystal X-ray diffraction studies reveal monomeric, six-coordinate structures. The thermal stabilities and vapor phase transport properties of these new complexes are considerably greater than those of conventional solid zinc metal-organic chemical vapor deposition (MOCVD) precursors. One of the complexes in the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentadionato)(N,N'-diethylethylenediamine)zinc, is particularly effective in the growth of thin films of the transparent conducting oxide Zn-In-Sn-O (ZITO) because of its superior volatility and low melting point of 64 degrees C. ZITO thin films with In contents ranging from 40 to 70 cation % (a metastable phase) were grown by low-pressure MOCVD. These films exhibit conductivity as high as 2900 S/cm and optical transparency comparable to or greater than that of commercial Sn-doped indium oxide (ITO) films. ZITO films with the nominal composition of ZnIn(2.0)Sn(1.5)O(z)() were used in fabrication of polymer light-emitting diodes. These devices exhibit light outputs and current efficiencies almost 70% greater than those of ITO-based control devices.     

Synthesis, characterization, and thermal properties of homoleptic rare-earth guanidinates: promising precursors for MOCVD and ALD of rare-earth oxide thin films

Eight novel homoleptic tris-guanidinato complexes M[(N(i)Pr)(2)CNR(2)](3) [M = Y (a), Gd (b), Dy (c) and R = Me (1), Et (2), (i)Pr (3)] have been synthesized and characterized by NMR, CHN-analysis, mass spectrometry and infrared spectroscopy. Single crystal structure analysis revealed that all the compounds are monomers with the rare-earth metal center coordinated to six nitrogen atoms of the three chelating guanidinato ligands in a distorted trigonal prism geometry. With the use of TGA/DTA and isothermal TGA analysis, the thermal characteristics of all the complexes were studied in detail to evaluate their suitability as precursors for thin film deposition by MOCVD and ALD. The (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) showed excellent thermal characteristics in terms of thermal stability and volatility. Additionally, the thermal stability of the (i)Pr-Me(2)N-guanidinates of Y and Dy (1a, c) in solution was investigated by carrying out NMR decomposition experiments and both the compounds were found to be remarkably stable. All these studies indicate that (i)Pr-Me(2)N-guanidinates of Y, Gd and Dy (1a-c) have the prerequisites for MOCVD and ALD applications which were confirmed by the successful deposition of Gd(2)O(3) and Dy(2)O(3) thin films on Si(100) substrates. The MOCVD grown films of Gd(2)O(3) and Dy(2)O(3) were highly oriented in the cubic phase, while the ALD grown films were amorphous.     

Synthesis,characterization, and thermal properties of novel silicon 1,1,3,3-tetramethylguanidinate derivatives and use as single-source chemical vapor deposition precursors

A series of chemical vapor deposition (CVD) precursors have been synthesized by a single-step reaction of 1,1,3,3-tetramethylguanidine and a variety of silicon chlorides. The structures of the 1,1,3,3-tetramethylguanidinate-based compounds were verified by ¹H NMR, ¹³C NMR, XPS, EI-MS, and elemental analysis. The thermal stability, transport behavior, and vapor pressures of these compounds were evaluated by simultaneous thermal analyses (STA). These compounds are highly stable and those in liquid form are very volatile. Silicon carbonitride (SiCN) thin films were prepared by using bis (tetramethylguanidine)-dimethyl-silane as the precursor in helicon wave plasma chemical vapor deposition (HWP-CVD). The properties of the films were investigated by SEM, AFM, and XPS. The results showed that the films have good uniformities, low friction coefficient, and high hardness, enabling the films for fabrication of semiconductor devices.     

Encapsulating bis(beta-ketoiminato) polyethers. Volatile, fluorine-free barium precursors for metal-organic chemical vapor deposition

The synthesis, characterization, and incorporation in volatile metal-organic chemical vapor deposition (MOCVD) precursors of a new class of linked beta-ketoiminate-polyether-beta-ketoiminate ligands is presented. These ligands are designed to encapsulate alkaline-earth cations having low charges and large ionic radii. Barium complexes having the general formula Ba[(RCOCHC(R')N)2(R")] (R = tert-butyl or CF3; R' = tert-butyl, methyl, or CF3; R" = -(CH2CH2O)4CH2CH2- or -(CH2CH2O)5CH2CH2)-) were prepared and characterized by 1H and 13C NMR spectroscopy, elemental analysis, and mass spectrometry. Single-crystal X-ray diffraction analysis of 2,2,5,25,28,28-hexamethyl-9,12,15,18,21-pentaoxa-4,25-diene-6,24- diimino-3,27-pentacosadionatobarium(II) reveals a monomeric, nine-coordinate, tricapped trigonal prismatic coordination geometry. Single-crystal X-ray structural analysis of 1,1,1,24,24,24-hexafluoro-4,21-ditrifluoromethyl-8,11,14,17- tetraoxa-3,21-diene-5,20-diimino-2,23-tetracosadionatobarium(II).2DMSO reveals a monomeric, ten-coordinate, distorted tetracapped trigonal prismatic coordination geometry. Volatility data are presented for these barium complexes, demonstrating viability as MOCVD precursors. In addition, it is demonstrated that thin epitaxial films of BaTiO3 can be grown on (001) MgO by low-pressure MOCVD techniques using one of these barium complexes and Ti(dipivaloylmethanate)2(isopropoxide)2 as precursors.     

Tris(phosphino)borato silver(I) complexes as precursors for metallic silver aerosol-assisted chemical vapor deposition

A series of light- and air-stable tris(phosphino)borato silver(I) complexes has been synthesized, structurally and spectroscopically characterized, and implemented in the growth of low resistivity metallic silver thin films by aerosol-assisted chemical vapor deposition (AACVD). Of the four complexes in the series, [RB(CH2PR'2) 3]AgPEt3 (R = Ph (1, 3), (n)Bu (2, 4); R' = Ph (1, 2), (i)Pr (3, 4), complexes 1 and 2 have been characterized by single-crystal X-ray diffraction. Complex 2 represents a significant improvement over previously available nonfluorinated Ag precursors, owing to ease of handling and efficient film deposition characteristics. Thermogravimetric analysis (TGA) shows that the thermolytic properties of these complexes can be significantly modified by altering the ligand structure. Polycrystalline cubic-phase Ag thin films were grown on glass, MgO(100), and 52100 steel substrates. Ag films of thicknesses 3 microm, grown at rates of 14-18 nm/min, exhibit low levels of extraneous element contamination by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicate that film growth proceeds primarily via an island growth (Volmer-Weber) mechanism.     

Effects of ZnO Buffer Layer Thickness on Properties of MgxZn1-xO Thin Films Deposited by MOCVD

High-quality MgxZn1-xO thin films were grown on sapphire（0001 ） substrates with a ZnO buffer layer of different thicknesses by means of metal-organic chemical vapor deposition. Diethyl zinc, bis-cyclopentadienyl-Mg and oxygen were used as the precursor materials. The crystalline quality, surface morphologies and optical properties of the Mg, Zn1-xO films were investigated by X-ray diffraction, atomic force microscopy and photoluminescence spectrometry. It was shown that the quality of the MgxZn1-xO thin films depends on the thickness of the ZnO buffer layer and an Mg, Zn1-xO thin film with a ZnO buffer layer whose thickness was 20 nm exhibited the best crystal-quality, optical properties and a flat and dense surface.     

Growth mechanism of textured MgO thin films via SSCVD

Magnesium oxide thin films have been deposited with use of single source chemical vapor deposition (SSCVD). The resultant films were examined by using transmission electron microscopy, X-ray texture analysis, and pole figure analysis. Due to the nature of the chemical reactions occurring at the surface during SSCVD growth, which result in a high growth rate/low flux environment, films of (111) orientation have been achieved without an amorphous underlayer, an unusual result for films of this orientation. Moreover the films have a strong degree of biaxial texturing in the x-y plane as found with X-ray texture analysis. These findings have important implications for buffer layers in perovskite thin film devices. The mechanism producing these structures has been revealed by using TEM and is discussed here.     

Nickel(II) complexes of N-(dialkylcarbamothioyl)-4-nitrobenzamide as single-source precursors for the deposition of nanostructured nickel sulfide thin films by chemical vapor deposition

Nickel(II) complexes of N-(di-alkyl-carbamothioyl)-4-nitrobenzamide (alkyl?=?ethyl or n-propyl) have been synthesized and characterized by infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, and mass spectrometry. The structures of bis[N-(diethylcarbamothioyl)-4-nitrobenzamide]nickel(II) (2a) and bis[N-(dipropylcarbamothioyl)-4-nitrobenzamide]nickel(II) (2b) have been determined by X-ray crystallography. FTIR and NMR of the nickel complexes showed the absence of the N–H proton resonance and the N–H stretch and shift of ν _C=O and ν _C=S as expected. Both complexes have been used as single-source precursors for the deposition of nickel sulfide nanostructured thin films by aerosol-assisted chemical vapor deposition. The nanostructured thin films were characterized by X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and atomic force microscopy.     

Possibilités d'obtention de dépôts dans le système céramique ti-v-c-n à partir de sources moléculaires

Monometallic and heterobtmetallic titanium and vanadium compounds were prepared and studied as precursors to the chemical vapor deposition (CVD) of carbide and nitride ceramic thin films. Their thermal properties are discussed according to the chemical environment of the metal atom and their CVD behavior is studied. Two of them, CpTiCl₂N(SiMe₃)₂ and Cp₂VMe₂, are applied to the deposition of thin films within the Ti-V-C-N quaternary system.     

High-performance,solution-processed organic thin film transistors from a novel pentacene precursor

The Lewis acid-catalyzed Diels-Alder reaction of the organic semiconductor pentacene with N-sulfinylacetamide yields a soluble adduct. Spin-coated thin films of this adduct undergo solid-phase conversion to form thin films of pentacene at moderate temperatures. Organic thin film transistors fabricated by spin-coating this adduct, followed by thermal conversion to pentacene, exhibit the highest mobility reported to date for a solution-processed organic semiconductor.     

Role of Anionic Backbone in NHC-Stabilized Coinage Metal Complexes: New Precursors for Atomic Layer Deposition**

Cu and Ag precursors that are volatile, reactive, and thermally stable are currently of high interest for their application in atomic-layer deposition (ALD) of thin metal films. In pursuit of new precursors for coinage metals, namely Cu and Ag, a series of new N-heterocyclic carbene (NHC)-based Cu^I and Ag^I complexes were synthesized. Modifications in the substitution pattern of diketonate-based anionic backbones led to five monomeric Cu complexes and four closely related Ag complexes with the general formula [M(^tBuNHC)(R)] (M=Cu, Ag; ^tBuNHC=1,3-di-tert-butyl-imidazolin-2-ylidene; R=diketonate). Thermal analysis indicated that most of the Cu complexes are thermally stable and volatile compared to the more fragile Ag analogs. One of the promising Cu precursors was evaluated for the ALD of nanoparticulate Cu metal deposits by using hydroquinone as the reducing agent at appreciably low deposition temperatures (145–160 °C). This study highlights the considerable impact of the employed ligand sphere on the structural and thermal properties of metal complexes that are relevant for vapor-phase processing of thin films.     

Deposition of Silicon Carbide Thin Films from 1,1-Dimethyl-1-Silacyclobutane

1,1-Dimethyl-1-silacyclobutane was used as a single-source precursor to deposit SiC thin films on Si(100) and Si(111) by low-pressure chemical vapor deposition (LPCVD). Polycrystalline β-SiC thin films were grown at temperatures 1100 and 1200°C. At temperatures between 950 and 1100°C, amorphous thin films of silicon carbide were obtained. The films were studied by X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), and electron diffraction (ED).     

Thermal analysis and vapour pressure of a new series of tungsten(VI) oxo-alkoxide-β-ketoesterate complex precursors for the chemical vapour deposition of tungsten oxide

A new series of tungsten complexes, tungsten(VI) oxo-alkoxide-β-ketoesterate complexes have been synthesized and characterized by infrared and NMR spectroscopy. Thermogravimetric analysis has been carried out on the complexes as a function of temperature, and isothermally as a function of time. Based on the thermal analysis data, these complexes are evaluated for their suitability as precursors for the chemical vapour deposition of tungsten oxide thin films. The vapour pressure of these precursors is estimated using the Langmuir equation.     

Chemical Vapor Deposition of Phase‐Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors

Homoleptic uranium(IV) amidate complexes have been synthesized and applied as single‐source molecular precursors for the chemical vapor deposition of UO₂ thin films. These precursors decompose by alkene elimination to give highly crystalline phase‐pure UO₂ films with an unusual branched heterostructure.     

Design of precursors for the CVD of inorganic thin films

Applications of inorganic thin films in the electronics industry have spurred activity in the area of chemical vapor deposition (CVD). This article discusses the increasingly sophisticated design strategies for precursor complexes through a series of case studies on CVD of metal oxide and metal nitride films.     

Effects of the polarizability and packing density of transparent oxide films on water vapor permeation

The tin oxide and silicon oxide films have been deposited on polycarbonate substrates as gas barrier films, using a thermal evaporation and ion beam assisted deposition process. The oxide films deposited by ion beam assisted deposition show a much lower water vapor transmission rate than those by thermal evaporation. The tin oxide films show a similar water vapor transmission rate to the silicon oxide films in thermal evaporation but a lower water vapor transmission rate in IBAD. These results are related to the fact that the permeation of water vapor with a large dipole moment is affected by the chemistry of oxides and the packing density of the oxide films. The permeation mechanism of water vapor through the oxide films is discussed in terms of the chemical interaction with water vapor and the microstructure of the oxide films. The chemical interaction of water vapor with oxide films has been investigated by the refractive index from ellipsometry and the OH group peak from X-ray photoelectron spectroscopy, and the microstructure of the composite oxide films was characterized using atomic force microscopy and a transmission electron microscope. The activation energy for water vapor permeation through the oxide films has also been measured in relation to the permeation mechanism of water vapor. The diffusivity of water vapor for the tin oxide films has been calculated from the time lag plot, and its implications are discussed.     

Low-Pressure Chemical Vapor Deposition of Silicon Carbide Thin Films from Organopolysilanes

(Me₃Si)₂SiMe₂, (Me₃Si)₃SiMe and (Me₃Si)₄Si were used as precursors for the deposition of polycrystalline β-SiC thin films on silicon substrates at 1000–1200°C in a low-pressure hot-wall chemical vapor deposition reactor. The thin films were analyzed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy.