Metal-organic Chemical Vapor Deposition Precursors Research Articles

Towards the MOCVD’s paradise: Thermodynamics of phase transitions of new scandium precursors

Scandium complexes with β-diketonate ligands are valuable precursors for the metal–organic chemical vapour deposition (MOCVD) of scandia based materials. The technology has been constantly developing and demanding novel precursors with accurately defined thermal properties, which could be used in MOCVD as well as related gas phase processes. Two new complexes with 1,1-difluoroacetylacetone (dfac) and 5,5,6,6,6-pentafluorohexane-2,4-dione (5Fac) have been synthesized, isolated, and characterized. The volatility and condensed phase behaviour including thermal stability and phase transitions of the obtained compounds have been studied; the saturated vapour pressures over crystalline Sc(dfac)3 and liquid Sc(5Fac)3 complexes have been measured. As a result, the standard molar thermodynamic characteristics of melting, sublimation, and vaporization processes have been calculated. Thermal properties of these compounds have been compared with literature data on scandium(III) β-diketonates already used as MOCVD precursor. These new compounds can be successfully used as precursors in the gas-phase deposition processes, and the set of obtained thermodynamic data can help in choosing the optimal deposition conditions.

In Pursuit of Next Generation N-Heterocyclic Carbene-Stabilized Copper and Silver Precursors for Metalorganic Chemical Vapor Deposition and Atomic Layer Deposition Processes

Volatile, reactive, and thermally stable organometallic copper and silver complexes are of significant interest as precursors for the metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) of ultra-thin metallic films. Well-established CuI and AgI precursors are commonly stabilized by halogens, phosphorous, silicon, and oxygen, potentially leading to the incorporation of these elements as impurities in the thin films. These precursors are typically stabilized by a neutral and anionic ligand. Recent advancements were established by the stabilization of these complexes using N-heterocyclic carbenes (NHCs) as neutral ligands. To further enhance the reactivity, in this study the anionic ligand is sequentially changed from β-diketonates to β-ketoiminates and β-diketiminates, yielding two new CuI and two new AgI NHC-stabilized complexes in the general form of [M(NHC) (R)] (M = Cu, Ag; R = β-ketoiminate, β-diketiminate). The synthesized complexes were comparatively analyzed in solid, dissolved, and gaseous states. Furthermore, the thermal properties were investigated to assess their potential application in MOCVD or ALD. Among the newly synthesized complexes, the β-diketiminate-based [Cu(tBuNHC) (NacNacMe)] was identified to be the most suitable candidate as a precursor for Cu thin film deposition. The resulting halogen-, oxygen-, and silicon-free CuI and AgI precursors for MOCVD and ALD applications are established for the first time and set a new baseline for coinage metal precursors.

Conformal Growth of Hexagonal Boron Nitride on High-Aspect-Ratio Silicon-Based Nanotrenches

We successfully accomplished the conformal growth of sp2-hybridized few-layer h-BN over an array of Si-based nanotrenches with a 45 nm pitch and an aspect ratio of ∼7:1 by using the pulsed-mode metal–organic chemical vapor deposition (MOCVD) method. Surface-sensitive X-ray absorption fine structure spectroscopy and density functional theory calculations revealed that the B–O bonds formed on the noncatalytic SiO2 surface act as nucleation sites for the subsequential formation of mixed sp2- and sp3-hybridized BON2 and BN3 at the very initial stage of the pulsed-mode injection of MOCVD precursors, enabling the conformal growth of few-layer sp2-hybridized h-BN with an excellent step coverage. We believe that these results can provide a broad avenue for the implementation of fascinating two-dimensional layered materials for current state-of-the-art three-dimensional Si-based nanoscale architectures, overcoming the downscaling limits.

A Review of Recent Progress in β‐Ga2O3 Epitaxial Growth: Effect of Substrate Orientation and Precursors in Metal–Organic Chemical Vapor Deposition

Gallium oxide (Ga2O3) is a highly promising ultrawide‐bandgap semiconductor for power electronics that emerged about a decade ago. Epitaxial growth Ga2O3 at the small scale is demonstrated. In order to develop scalable manufacturing of high‐performance epitaxial structures, in‐depth understanding of the fundamental growth processes, control parameters, and mechanism is imperative. This review discusses the recent progress in epitaxial growth of β‐Ga2O3 films and highlights challenges in obtaining high growth rate, low defects, and high carrier mobilities. Compared with the other epitaxy methods, metal–organic chemical vapor deposition (MOCVD) offers a wider growth window and precursor selection option, to minimize the tradeoff between crystal quality and growth rate. Growth rate is inversely proportional to temperature, within a certain temperature window, because of the unavoidable premature gas‐phase reactions and desorption of the highly volatile gallium suboxide (Ga2O) at elevated temperatures. Growth defects, background impurity incorporation, and carrier mobilities can be affected by the choice of MOCVD precursors, nucleation, and adsorption/desorption/diffusion of adatoms on substrate surfaces of different orientations, including the effect of growing on cleavage and noncleavage planes. This review summarizes the current status of the epitaxial growth of β‐Ga2O3 and analyzes the major factors that enhance mobility and reduce background doping concentration. The insights gained help advance the manufacturability of device‐grade epitaxial thin films.

Volatile Iridium and Platinum MOCVD Precursors: Chemistry, Thermal Properties, Materials and Prospects for Their Application in Medicine

Interest in iridium and platinum has been steadily encouraged due to such unique properties as exceptional chemical inertia and corrosion resistance, high biological compatibility, and mechanical strength, which are the basis for their application in medical practice. Metal-organic chemical vapor deposition (MOCVD) is a promising method to fabricate Ir and Pt nanomaterials, multilayers, and heterostructures. Its advantages include precise control of the material composition and microstructure in deposition processes at relatively low temperatures onto non-planar substrates. The development of MOCVD processes is inextricably linked with the development of the chemistry of volatile precursors, viz., specially designed coordination and organometallic compounds. This review describes the synthesis methods of various iridium and platinum precursors, their thermal properties, and examples of the use of MOCVD, including formation of films for medical application and bimetallics. Although metal acetylacetonates are currently the most widely used precursors, the recently developed heteroligand Ir(I) and Pt(IV) complexes appear to be more promising in both synthetic and thermochemical aspects. Their main advantage is their ability to control thermal properties by modifying several types of ligands, making them tunable to deposit films onto different types of materials and to select a combination of compatible compounds for obtaining the bimetallic materials.

Volatile asymmetric fluorinated (O^N)-chelated palladium complexes: From ligand sources to MOCVD application

The work deals with the volatile asymmetric palladium complexes of β-ketoiminate-type as a new direction to design the effective partially fluorinated (O^N)-chelated precursors for metal–organic chemical vapor deposition (MOCVD). To determine the effect of the substituent on the donor nitrogen atom, [Pd(CF3COCHCN(R)CH3)2]2 complexes with R = CH3 (Mei-tfac) and N(CH3)2 (dmht) were synthesized and characterized by elemental analysis, IR and NMR spectroscopy. The molecular and crystal structures of the complexes as well as the initial ligand sources HMei-tfac and Hdmht were determined by single-crystal XRD. The obtained a new crystallographic and thermal (TG/DTA) information combined with the crystal lattice energy calculations allowed to reveal the features of the N-substituted fluorinated complexes in comparison with their non-fluorinated analogs. The possibility of using the proposed compounds as MOCVD precursors was experimentally confirmed.

Inverted Lattice-Matched Triple Junction Solar Cells With 1.0 eV GaInNAsSb Subcell by MOCVD/MBE Hybrid Growth

In this paper, lattice-matched GaInP/GaAs/GaInNAsSb 3-junction (3J) solar cells were fabricated using a hybrid growth technique consisting of metalorganic chemical vapor deposition (MOCVD) for the upper two subcells and molecular beam epitaxy (MBE) for the bottom cell. In the normal upright configuration, the MBE-grown GaInNAsSb solar cells often suffer from unintentional hydrogen incorporation due to the pyrolysis of MOCVD precursors during the growth of other subcells, which can lead to a degradation of the cell performance of GaInNAsSb subcell. In contrast, we studied the inverted growth sequence in order to avoid hydrogen incorporation. Then, we applied post-growth annealing to improve the carrier collection efficiency of GaInNAsSb bottom cell. The annealing effectively improved the carrier collection and increased the quantum efficiency of GaInNAsSb bottom cell in the present inverted 3J structure, whereas no significant disadvantages for the top and middle cells were observed. As a result, we achieved external quantum efficiency beyond 90% in 1.0 eV GaInNAsSb bottom cells with thicknesses of 1.5 and 2.0 μ m, and successfully demonstrated high enough photocurrents, fulfilling the current matching condition in the 3J solar cells.

Iron(III) β-diketonates: CVD precursors for iron oxide film formation

Complexes [Fe(β-diketonate)3] (β-diketonate = 2-acetylcyclopentanoate (3a), = 2-acetylcyclohexanoate (3b), = 4,4-dimethyl-1-phenyl pentanedionate (3c)) were synthesized by the reaction of FeCl3 with the respective β-diketones in presence of NaOH. The molecular structures of 3a and 3c in the solid state are discussed, confirming an octahedral coordination sphere at Fe(III) setup by the three bidentate-bonded β-diketonato ligands. Variation of the β-diketonato ligands allowed to influence the thermal behavior and vapor pressure of the complexes. TG-MS ( = Thermo Gravimetry-Mass Spectrometry) studies, exemplarily carried out on 3a, confirmed the release of the β-diketonate ligands. Complexes 3a–c were applied as MOCVD (=Metal-Organic Chemical Vapor Deposition) precursors for the deposition of Fe2O3 thin films on silicon substrates. It was found that with 3a,b, conformal and dense carbon-free γ- and α-Fe2O3 layers were produced at 450 °C, which was verified by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photon spectroscopy.

Synthesis of Cu–Cr diketo, sublimable, eutectic composite complex, rod crystals from LDH as suitable MOCVD precursor of CuCr2O4 catalysts upon ceramic preforms for N2O decomposition

Metal-acteylacetonates are important sublimable metal-organic precursors for metal-oxide thin film formation over solid preforms by MOCVD (Metal Organic Chemical Vapour Deposition) technique. Mixed-metal-acetylacetonates (MMAA) are suitable starting materials for mixed metal nano-oxidic thin film formation through such facile routes. Layered Double Hydroxides (LDH) of suitable metal ion combination can perform as appropriate starting base for neutralisation by enol form of 2,4-pentanedione or acteylacetonate tautomer ligands to obtain such MMAA. In this paper synthesis of composite crystals of Cu(II)/Cr(III) acetylacetonates (CCAA) is reported by the reaction of Cu–Cr-LDH with acetylacetone. The products were characterized by various different techniques. The surface area and pore volume analysis of the crystals showed the formation of nanopores in the compound. TEM analysis confirmed that the inner core of the nanoporous crystals of Cu(acac)2 was covered by coating of poorly crystallised Cr(acac)3 and they together form the composite crystals, and they together form the composite crystals. Due to eutectic mixture formation the melting point of CCAA lies in between the melting points of individual components Cu(acac)2 and Cr(acac)3 and shows sublimability, a property important for the formation of MOCVD films. The composite was used for CuCr2O4 spinel mixed oxide films formation over solid ceramic honeycomb monolithic substrates. Application prospects of the route in the field of catalysis is high as it can directly combine the benefits of mixed metal oxide catalysis and structured supports without the involvement of a third component. In this work the performance of such a catalytic device has been tested for low temperature decomposition of high Global Warming Potential (GWP) gas N2O to N2 and O2.

Manganese half-sandwich complexes as metal-organic chemical vapor deposition precursors for manganese-based thin films

The synthesis of compounds [Mn(η5–C5H4SiMe3)(CO)3] (1), [Mn(η5–C5H3-1-SiMe3-3-Me)(CO)3] (2), [Mn(η5–C5H4tBu)(CO)3] (3), [Mn(η5–C5Me5)(CO)3] (4) and [Mn(η5–C5H7)(CO)3] (5) and their potential use as metal-organic chemical vapor deposition (MOCVD) precursors for the deposition of manganese-based layers is reported. The thermal behavior of 1–5 was studied by thermogravimetry showing that these compounds evaporate in the temperature range of 363–498K depending on the cyclopentadienyl substituents and the type of pentadienyl used. Vapor pressure measurements indicate that all compounds possess vapor pressures between 60 and 630Pa at 353K. Compounds 1–5 could be successfully applied in manganese-based film deposition without activation steps prior to the MOCVD experiments. The as-deposited thin layers were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and X-ray powder diffraction. Under comparatively mild conditions, whereas 5 possesses the lowest deposition temperature (553K), dense and conformal layers with growth rates up to 7.0nmmin−1 (5) could be deposited. Metal carbonyls 1 and 2 featuring a SiMe3 group produced Si-containing manganese-based films. The as-deposited layers from 1, 2, 4 and 5 contain carbon impurities (5–8.9mol-%), while the films from 3 are carbon-free. The layers from 1 and 2 consist of mainly manganese silicate and manganese oxide, whereas those obtained from 3 to 5 are composed of manganese oxides.

Sb Doped GeSn Growth by MOCVD with Newly Employed Source Gases

We demonstrated MOCVD (Metal Organic Chemical Vapor Deposition) GeSn growth co-doped with Sb. The Sb doping accelerated the Sn incorporation in the GeSn epitaxial film. The Sn and Sb concentrations were 6.6% and 0.5%, respectively. We consider the surfactant effect by the Sb as well as atmospheric H2 suppress the surface migration and therefore the precipitation of Sn. 1. Introduction GeSn is a promising material for large scale optoelectronic integrated devices on the Si platform [1]. It is reported that GeSn with Sn concentration more than approximately 10% has direct bandgap and emits light efficiently. In addition, GeSn is also expected to improve the performance of MOSFET, when it is used as a material for the channel or source/drain. In order to enjoy the high performance of various GeSn based devices, it is necessary to achieve both high Sn concentration and high crystallinity. However, it has been difficult to increase Sn concentration, because the solid solubility limit of Sn is approximately 1%. Higher Sn concentration than the solubility limit has been demonstrated by MBE at extremely low growth temperature; however, the low temperature growth generally results in the poor crystal quality. Donor or acceptor doping in the GeSn layer has not been reported so much yet, although it should be indispensable for the device application. In this study, we examined MOCVD GeSn growth with Sb doping and found that the high concentration Sn and Sb doping can be achieved simultaneously. 2. Experiments In our experiments, we used tertiarybutylgermane (t-C4H9GeH3) and tetra-ethyl tin (C2H5)4Sn as MOCVD precursors with H2 carrier gas. The Sb is doped from the atmosphere with residual triisopropyl-antimony [(i-C3H7)3Sb]. These newly employed precursors are significantly safer than conventional Ge2H6 and SnH4 because of their non-pyrophoric and non-explosive characteristics. We used Ge(001) as the substrate. The deposition was carried out in 30 Torr atmosphere for 120 min at 320-360°C. The injection rate of the Ge and Sn precursors were controlled between approximately 3.5 × 10−6 and 1.4 × 10−4 mol/min. H2 supply was at 20-40 sccm. The Sn and Sb concentrations were measured by the combination of RBS and SIMS. TEM observation was also carried out for the evaluation of the crystal quality. 3. Results and Discussion Figure 1 shows the depth profiles of Sn and Sb concentration in the epitaxial film. Here, the (Sn+Sb) profile was determined by RBS first. Then, the Sn/Sb ratio was measured by SIMS. The Sn concentration close to the epitaxial interface may be more than 10% and then decreases to the constant of approximately 6.6%, while the Sb concentration is quite uniform along the depth at approximately 0.5%. The surface segregation for Sn and Sb should be the artifacts of the measurement. No obvious defects or precipitations were found by the TEM observation. The Sn concentration is much higher than that obtained without Sb doping; therefore, we believe the Sb doping promoted the Sn incorporation in the film. It is also remarkable that Sb was doped up to such high concentration without precipitation at this relatively high growth temperature. We have verified the existence of H2 in the MOCVD atmosphere promoted the Sn incorporation in the GeSn film, probably due to the surfactant effect. Sb might bring the similar surfactant effect for the GeSn growth. The H2 suppress the Sn surface migration therefore suppress the precipitation [2]. It has been also reported that Sb during the InGaAsN growth lowers surface energy and suppress both surface migration and island formation [3]. The surfactant effects provided by H2 and Sb, in which the surface migration and therefore the precipitation were suppressed similar to the case of the low temperature growth, might promote the Sn and Sb incorporation beyond the solubility limits. 4. Conclusions In this study, we have demonstrated high concentration Sn and Sb incorporation in the epitaxial Ge grown by MOCVD. The Sn and Sb concentrations were 6.6% and 0.5%, respectively. These high concentration may be due to the surfactant effect of both H2 and Sb.

Half-sandwich cobalt complexes in the metal-organic chemical vapor deposition process

A series of cobalt half-sandwich complexes of type [Co(η5-C5H5)(L)(L′)] (1: L, L′=1,5-hexadiene; 2: L=P(OEt)3, L′=H2CCHSiMe3; 3: L=L′=P(OEt)3) has been studied regarding their physical properties such as the vapor pressure, decomposition temperature and applicability within the metal-organic chemical vapor deposition (MOCVD) process, with a focus of the influence of the phosphite ligands. It could be shown that an increasing number of P(OEt)3 ligands increases the vapor pressure and thermal stability of the respective organometallic compound. Complex 3 appeared to be a promising MOCVD precursor with a high vapor pressure and hence was deposited onto Si/SiO2 (100nm) substrates. The resulting reflective layer is closed, dense and homogeneous, with a slightly granulated surface morphology. X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of metallic cobalt, cobalt phosphate, cobalt oxide and cobalt carbide.

Metal organic precursor effect on the properties of SnO2 thin films deposited by MOCVD technique for electrochemical applications

Tin dioxide (SnO2) thin films are deposited by metal organic chemical vapor deposition (MOCVD) on Si substrates from three commercial metal organic precursors. The morphology and the microstructure of the films are observed by field emission gun-scanning electron microscopy (FEG-SEM). The films are dense and made of crystallites with a nanometer size. The structural properties of the films are assessed by grazing incidence X-ray diffraction (GIXRD). A tetragonal SnO2 phase is observed in the deposited thin films with various texturations as a function of the metal organic precursor used for the deposition. Chemical characterizations of the thin films are also carried out by Fourier transformed infrared spectroscopy (FT-IR) and by X-ray photoelectron spectroscopy (XPS). Finally, the observed morphological, chemical and structural modifications induce changes in the electrical properties of the film. Results are discussed and indicate that the electrical properties of the synthesized SnO2 thin films differ as a function of the MOCVD precursor used for the deposition. Therefore, their electrochemical behavior is modified which influences the grafting of organic molecules to synthesize and develop novel hybrid materials sensors.

Hexacarbonyl (Trimethylsilyl Ethyne) Dicobalt as MOCVD Precursor for Thin Cobalt Layer Formation

AbstractThe low melting Co0 source [Co2(CO)6(η2‐Me3SiC≡CH)] (3) was prepared as a precursor system for the metal‐organic chemical vapor deposition (MOCVD) of cobalt. The synthesis of 3 was realized by the reaction of trimethylsilyl acetylene (2) with dicobalt octacarbonyl (1) in n‐hexane at ambient temperature. Vapor pressure measurements and TG‐MS analysis were performed revealing the suitability of 3 in the CVD process. Cobalt layers formed in a vertical cold wall CVD reactor were characterized by SEM, EDX, and XPS. The appropriate metallic films consist of a mixture of cobalt and cobalt oxide.

ChemInform Abstract: Lanthanide Amidinates and Guanidinates in Catalysis and Materials Science: A Continuing Success Story

AbstractReview: 72 refs.

Organophosphine/phosphite‐stabilized silver(I) complexes bearing N‐hydroxysuccinimide ligand: synthesis, solid state structure and their potential use as MOCVD precursors

Six organophosphine/phosphite‐stabilized silver(I) N‐hydroxysuccinimide complexes of type [C4H4NO3Ag⋅Ln] (L = PPh3; n = 1, 2a; n = 2, 2b; L = P(OEt)3; n = 1, 2c; n = 2, 2 d; L = P(OMe)3; n = 1, 2e; n = 2, 2f) were prepared. These complexes were obtained in high yields and characterized by elemental analysis, 1H NMR, 13 C{1H} NMR and IR spectroscopy, respectively. The molecular structure of 2b has been determined by X‐ray single‐crystal analysis in which the silver atom is in a distorted tetrahedral geometry. An interstitial methanol solvent molecule is hydrogen bonded to the oxygen atom of N‐hydroxysuccinimide molecule. Complex 2f was used to deposit silver films by metal‐organic chemical vapor deposition (MOCVD) for the first time. The silver film obtained at 480 °C is dense and homogeneous, which is composed of many well‐isolated, granular particulates spreading all over the substrate surface. Copyright © 2012 John Wiley & Sons, Ltd.

Lanthanide amidinates and guanidinates in catalysis and materials science: a continuing success story

Today the rare-earth elements play a critical role in numerous high-tech applications. This is why various areas of rare-earth chemistry are currently thriving. In organolanthanide chemistry the search for new ligand sets which are able to satisfy the coordination requirements of the large lanthanide cations continues to be a hot topic. Among the most successful approaches in this field is the use of amidinate and guanidinate ligands of the general types [RC(NR')(2)](-) (R = H, alkyl, aryl; R' = alkyl, cycloalkyl, aryl, SiMe(3)) and [R(2)NC(NR')(2)](-) (R = alkyl, SiMe(3); R' = alkyl, cycloalkyl, aryl, SiMe(3)), which can both be regarded as steric cyclopentadienyl equivalents. Mono-, di- and trisubstituted lanthanide amidinate and guanidinate complexes are all readily available. Various rare earth amidinates and guanidinates have turned out to be very efficient homogeneous catalysts e.g. for the polymerization of olefins and dienes, the ring-opening polymerization of cyclic esters or the guanylation of amines. Moreover, certain alkyl-substituted lanthanide tris(amidinates) and tris(guanidinates) were found to be highly volatile and are thus promising precursors for ALD (= atomic layer deposition) and MOCVD (= metal-organic chemical vapor deposition) processes in materials science, e.g. for the production of lanthanide nitride thin layers. This tutorial review covers the continuing success story of lanthanide amidinates and guanidinates which have undergone an astonishing transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors within the past 10 years.

Sc2O3, Er2O3, and Y2O3 thin films by MOCVD from volatile guanidinate class of rare-earth precursors

Alternative novel precursor chemistries for the vapor phase deposition of rare-earth (RE) oxide thin films were developed by synthesising the homoleptic guanidinate compounds tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-scandium(III) [Sc(DPDMG)(3)] (1), tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-erbium(III), [Er(DPDMG)(3)] (2) and tris(N,N'-diisopropyl-2-dimethylamidoguanidinato)-yttrium(III), [Y(DPDMG)(3)] (3). All three compounds are monomeric as revealed by single crystal X-ray diffraction (XRD) analysis, nuclear magnetic resonance (NMR) and electron impact mass spectrometry (EI-MS). The thermal analysis revealed that the compounds are volatile and very stable under evaporation conditions. Therefore the complexes were evaluated as precursors for the growth of Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films, respectively, by metal-organic chemical vapor deposition (MOCVD). Uniform Sc(2)O(3), Er(2)O(3) and Y(2)O(3) films on Si(100) substrates with reproducible quality were grown by MOCVD by the combination of the respective guanidinate precursors and oxygen in the temperature range 350-700 °C. The structural, morphological, compositional and electrical properties of the films were investigated in detail. The most relevant film properties are highlighted in relation to the distinct advantages of the novel precursor chemistries in comparison to the commonly used literature known RE precursors. This study shows that compounds 1-3 are very good precursors for MOCVD yielding Sc(2)O(3), Er(2)O(3) and Y(2)O(3) thin films which are stoichiometric and display suitable electrical properties for their potential use as high dielectric constant (high-k) materials.

Ce(IV) Complexes with Donor-Functionalized Alkoxide Ligands: Improved Precursors for Chemical Vapor Deposition of CeO2

Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.

Chemical Vapor Deposition of Ni–C Films from Bis-(Ethylcyclopentadienyl) Nickel

Metal-organic chemical vapor deposition (MOCVD) is widely used for deposition of various nickel-containing coatings, such as catalytic nickel thin films and nanoparticles, nickel silicide alloys and magnetic carbon-nickel nanocomposite layers. Here we report preliminary results from an attempt to use bis-(ethylcyclopentadienyl) nickel [(EtCp)2Ni] as a precursor for MOCVD of Ni-C thin films in the (EtCp)2Ni-Ar and (EtCp)2Ni-H2-Ar reaction systems. Mechanism of precursor fragmentation was proposed on the basis of the results from a study of gaseous reaction products in the exhaust line of the reactor by means of mass-spectrometry. It was found that an introduction of hydrogen in the gas phase led to an increase in conversion rate of the precursor. Deposited films were analyzed by means of atomic force microscope (AFM), scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XFS). The effect of hydrogen on growth rate, composition, and morphology of the deposited Ni-C films were experimentally studied.