Vapor phase treatment of macroscopic formations of carbon nanotubes

Abstract

Provided is a composite of a CNT assembly including a plurality of carbon nanotubes (CNTs) and at least one metalcone material, the composite being tunable, by a vapor phase chemical modification, to adopt one or more collective properties selected from mechanical, chemical, physical or electrical properties.

Claims

1. A composite of a CNT assembly comprising a plurality of carbon nanotubes (CNTs), at least one metalcone material layer comprising at least one metalcone material directly non-covalently associated with said CNTs, and at least one hybrid organic-inorganic material non-metalcone layer having the structure:
—[[O.sub.b—(Si—R)].sub.m—[O—(Ti)-].sub.n—O.sub.a].sub.L—, wherein O.sub.a is an oxygen atom and O.sub.b is an oxygen atom, said at least one hybrid organic-inorganic material non-metalcone layer being positioned on the at least one metalcone material layer and is associated therewith via the oxygen atom designated O.sub.a or O.sub.b, the composite being made, by tandem molecular and atomic vapor phase chemical modification, wherein the tandem molecular and atomic vapor phase chemical modification comprises m number of molecular vapor deposition cycles and n number of atomic vapor deposition cycles, wherein each of m and n, independently, is between 1 and 50, wherein L is between 1 and 100, and wherein R is an organic component, forming a Si—C bond, the organic component being selected or modifiable to render the CNT assembly with one or more collective properties selected from the group consisting of mechanical, chemical, physical or electrical properties, wherein the CNT assembly is selected from the group consisting of CNT mats, CNT yarns, CNT fibers, CNT webs, carbon cloth and buckypaper.

2. The composite according to claim 1, wherein the at least one metalcone material is distributed over a surface of the plurality of CNTs in a continuous form, either fully engulfing the plurality of CNTs, or distributed over the plurality of CNTs in spaced apart regions.

3. The composite according to claim 1, being in a form of a multilayered structure, wherein the CNT assembly forms the inner-most part of the multilayered structure and each of the at least one metalcone material forms at least one layer on a surface of the CNT assembly.

4. The composite according to claim 1, wherein the at least one metalcone material is selected amongst metal alkoxides having a metal atom covalently bonded to at least one organic moiety or metal oxide having an oxygen atom forming an oxide or a hydroxide species.

5. The composite according to claim 1, wherein the at least one metalcone material layer comprises a plurality of metal atoms in-layer associated to each other, directly or via bridging atoms or organic ligands, wherein the plurality of metal atoms are further associated with one or more surface exposed hydroxides, oxides and/or alkoxide groups.

6. The composite according to claim 5, wherein the metal atoms are selected from the group consisting of Zn, Zr, Fe, Ti, V, Cu, Ni, Bi and W.

7. The composite according to claim 5, wherein the metal atoms are selected from the group consisting of Al, Ti, Zn, Fe, V, Ni, Cu and Cr.

8. The composite according to claim 5, wherein the metal atoms are selected from the group consisting of Ti, Al or Zn.

9. A process for manufacturing a composite of claim 1 comprising at least one CNT assembly and one or more material layers provided directly on the CNT assembly, the process comprising: forming by ALD a first material layer on the at least one CNT assembly; and forming one or more additional material layers on said first material layer by ALD, MLD, combined ALD/MLD or tandem ALD/MLD, wherein the first material layer comprises at least one metalcone and wherein the CNT assembly is part of a CNT macrostructure selected from a CNT mat, a CNT yarn, a CNT fiber, CNT web, a carbon cloth and a buckypaper.

10. The process according to claim 9, wherein at least one of the one or more material layers comprises at least one metalcone.

11. The process according to claim 10, wherein the metalcone precursor composition comprises at least one metal source and at least one hydroxyl precursor.

12. The process according to claim 9, comprising: treating a CNT assembly under ALD conditions with at least one metalcone precursor composition to form a first coating or film of at least one metalcone material on the surface of at least one CNT assembly; treating the CNT assembly one or more times under ALD, MLD or ALD/MLD conditions to form one or more additional material layers on the first coating or film.

13. The process according to claim 9, comprising: treating a CNT macrostructure under ALD conditions with at least one metalcone precursor composition to form a first coating or film of at least one metalcone material on the surface of at least one CNT assembly comprised in the macrostructure; treating the CNT macrostructure one or more times under ALD, MLD or ALD/MLD conditions to form one or more additional material layers on the first coating or film; wherein the first coating or film of the at least one metalcone material is non-covalently associated to the at least one CNT assembly.

14. The process according to claim 13, comprising treating the CNT macrostructure one or more times under ALD, MLD or ALD/MLD conditions to form a bilayer or a multilayered structure on the surface of the first coating or film, wherein each of the layers in the bilayer or multilayer is same or different, each optionally comprising at least one metalcone material.

15. The process according to claim 9, wherein the at least metalcone precursor composition comprises at least one metal source and one or more same or different ligand groups selected from at least one hydroxide precursor and optionally at least one organic alcohol material.

16. The process according to claim 15, wherein the at least one metal source is in the form of a metal salt or a metal complex.

17. The process according to claim 9, wherein the metalcone precursor composition comprises at least one metal source, at least one organic alcohol and at least one hydroxyl precursor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 depicts the methodology of the invention, utilizing vapor methodologies for tailoring CNT-based nanocomposite yarns including ALD, MLD, ALD-MLD, and tandem A/MLD.

(3) FIG. 2 depicts ALD/MLD deposition process for the inorganic-organic [—[O—(Si—R)]m-[—(Ti)—]n-O].sub.L hybrid thin film for trimethoxysilanesiloxane with R═N,N-dimethyl-3-aminopropyl, H.sub.2O, TiCl.sub.4 used as molecular precursors. Film deposited by L cycles of tandem ALD-MLD process with composition tuning by repeating n cycles of ALD and m cycles of MLD.

(4) FIGS. 3A-C depicts properties of thin films prepared by tandem Ti—Si A/MLD. FIG. 3A—Growth per cycle (GPC) for the process at 150° C.; FIG. 3B—Electrical tuning of Ti—Si thin films annealed films at 550, 750, and 1050° C. under Ar atmosphere vs. MLD-ALD super-cycle details (m/n). FIG. 3C—XPS analysis quantifying the relative contribution of Si.sup.3+ and Si.sup.4+ species. The oxidation state of Si suggests that Si—C functions as a reducing agent while TiO.sub.2 acts as an oxidant resulting in the formation of a sub-stoichiometric conductive Magnéli phase of Ti oxide.

(5) FIGS. 4A-C depicts tandem A/MLD for Ti—Si hybrid films deposited with various silane precursors. FIG. 4A—presents thickness vs. cycles (marker size in FIG. 4C represent maximal experimental error limit) and FIG. 4B growth per cycle (GPC) comparison for DE-AMTMS, DM-APTMS, APTMS and TMOS for 1:1 MLD:ALD process.

(6) FIG. 5 provides a depiction of a CNT mat comprising a plurality of CNT assemblies and treated according to embodiments of the present invention.

(7) FIG. 6 provides a zoom-in view of an assembly of CNTs according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(8) A combined methodology using MLD and ALD is presented where, for example, MLD, a hybrid organic-inorganic film is deposited for managing the surface properties of CNT mats and in the following step oxide layer is deposited by ALD for altering the mechanical properties of the assembly. Ethylene glycol (EG) and trimethyl aluminum (TMA) may be used for MLD for depositing a hybrid layer relying mostly on non-covalent attachment at the CNT surface. Water and TMA are used for a second deposition using ALD where cross-linking of the MLD deposited layer and additional oxide layer are formed. Alternative sequences are also disclosed and exemplified herein.

(9) The generality of the technology disclosed herein is depicted in FIG. 1. As shown, the technology provides a new platform for the construction of nanocomposite yarns based on CNT webs with the ability to design the overall materials qualities such as strength, durability, strain tolerance, electronic characteristics, as required for super capacitor applications, use as anodes, and surface properties such as hydrophilic/hydrophobic and permeability required for advanced membrane applications. Furthermore, utilizing layer-by-layer deposition of the composite matrix, applied to CNT web and to CNT mats (woven and non-woven), prior to yarn formation, enables to systematically vary the interface details and functionalities, and study the nanocomposite properties across scales, ranging from the molecular, nano, and macro scales, which results in significant insights, in addition to the direct impact originating from extending available materials and diversity.

(10) Merging the vapor phase methodologies presented herein with advanced deposition techniques, such as spatial ALD as disclosed herein enable scaling of the design principles applied at the atomic, and molecular levels principles to the macroscopic scale yielding tailored nanocomposite yarn materials.

(11) The technology involves several principles: (i) relying on CNT sources with high geometrical aspect ratios other than CNT powders or suspensions, drawn to CNT web structures, or CNT mats, and by (ii) customizing and merging atomic and molecular layer deposition chemistries with CNT web processing, including new tandem-catalytic A/MLD chemistry, and by (iii) utilizing emerging vapour phase methodology, spatial-A/MLD (S-A/MLD), for treatment of the CNT webs and CNT mats (woven and non-woven).

(12) One of the hallmarks of atomic and molecular layer deposition is the highly conformal, pin-hole free layers forms on a variety of substrates and nanosystems, including nanowires and nanotubes. This invention provides optimal surface coverage of the CNT bundles with the desired add-layer, which is the nanocomposite matrix component, deposited from the vapor phase. Vapor phase chemistry is utilized to overcome the difficulties encountered in introducing the matrix components (a) in the condensed phase, and (b) once the CNT webs are collapsed to the yarn structures. This allows to the tailoring of the relevant properties of the derived CNT-nanocomposite yarn materials.

(13) Key consideration to address is the type of vapor phase chemistries that are applied to the CNT webs and CNT mats (woven and non-woven) to ensure uniform surface modification with tight interface interactions between the CNTs and the deposited matrix. Here is a non-limiting list of considerations:

(14) (I) Hybrid Organic-Inorganic Matrix Deposited by MLD.

(15) The CNT web and CNT mats (woven and non-woven) that are uniformly coated with hybrid organic-inorganic layers, metalcones, which are metal alkoxide films that comprise of bi-, or tri-functional organic components such as bi-functional alcohols, covalently attached to inorganic metal component, yielding organic-inorganic (metal oxide) hybrid films with tunable surface and mechanical properties. Relying on MLD for uniform deposition of organic-inorganic hybrid layers on CNT webs and CNT mats (woven and non-woven) by MLD not only address the surface incompatibility of CNTs encountered for pure metal oxides, but also provides a handle for tuning the mechanical properties of deposited nanocomposite matrices by constructing in a layer-by-layer fashion hybrid organic-inorganic (MLD) and purely inorganic (ALD) superstructures by combined MLD-ALD processes. According to some embodiments of the present invention the hybrid layer is deposited establishing the required interfacing to the CNT surface, then an inorganic layer is deposited, and the sequence is repeated. Each step is independent of the other. According to other embodiments of the present invention, an A/MLD tandem catalytic process is employed where each sub-cycle catalyze the deposition of the complementary sub-cycle. MLD-ALD superstructures offers continuous tuning of the mechanical properties of the deposited layers ranging between polymer-like characteristics for all-MLD to oxide-like properties for all-ALD, and desired intermediate according to the MLD-ALD proportions of the process applied. for example hybrid Ti—EG—TiO.sub.2 is deposited by MLD-ALD (using TiCl.sub.4 as metal source and ethylene glycol and H.sub.2O precursors for the hybrid and pure oxide, respectively). CNT webs may be modified with Al—EG—Al.sub.2O.sub.3 super structures (using trimethylaluminum (TMA) can be used as metal source and ethylene glycol and H.sub.2O precursors for the hybrid and pure oxide, respectively), and\or Zn—EG-ZnO superstructures (using diethyl zinc as metal source and ethylene glycol and H.sub.2O precursors for the hybrid and pure oxide, respectively). A binding layer for CNT-composites with tailored surface functionalities, deposited bytandem A/MLD, may be used for surface decoration with free amines, protected amines, and any other functional groups.

(16) (II) Metal-Oxide Matrix Deposited by ALD.

(17) Farmer, D. et al. have demonstrated that single-walled CNT can be functionalized without degradation of their electronic properties by ALD treatment of NO2 and TMA, forming an adsorbed layer that mediate high quality, conformal, and smooth deposition of oxides. The present invention provides CNT webs and CNT mats (woven and non-woven) with maximal surface coverage of the CNTs. CNT-composites with stoichiometric oxides such as Al.sub.2O.sub.3, TiO.sub.2, ZnO, as well as non-stoichiometric oxides are provided for use as enhanced photocatalysis and conductive oxide.

(18) Implementation of Vapor Phase Chemistry to CNT Webs and CNT Mats (Woven and Non-Woven) by Customized A/MLD Reactor Setup

(19) The surface modification classes listed above, spanning, oxides, organic-inorganic hybrids, and combinations of inorganic binding layer with hybrid organic-inorganic overlayers provide a versatile platform for tailoring the CNT interfaces for designing the nanocomposite yarn materials with desired mechanical, electronic, and even photocatalytic properties such as self-cleaning.

(20) The combined strategy provided by the present invention overcomes the inherent difficulties associated with condensed phase treatments of high aspect ratio CNTs in the context of composite materials. Introduction of the advanced vapor phase chemistry capabilities to CNT webs and CNT mats (woven and non-woven) disclosed herein overcomes the problems usually encountered in tailoring a CNT-matrix composite by affording a uniform, complete surface interaction of the deposited matrix and CNT interfaces. The solution provided by the present invention to these issues is achieved by coupling appropriate vapor phase chemistry and applying A/MLD specifically to the CNT web region and CNT mats (woven and non-woven), prior to collapse of the CNTs. Importantly, obtaining optimal functionality of the high loading CNT-based nanocomposites, requires that the deposited matrix have a uniform, continuous, and maximal areal coverage over the CNT interfaces. Merging the vapor phase methodologies disclosed herein with advanced deposition techniques, such as spatial ALD as disclosed herein enable scaling of the design principles applied at the atomic, and molecular levels principles to the macroscopic scale yielding tailored nanocomposite yarn materials.

(21) Implementation of the Vapor Phase Chemistries to CNT Webs and CNT Mats (Woven and Non-Woven) by Spatial A/MLD

(22) Spatial ALD (S-ALD) is a variant of conventional. The uniqueness of S-ALD relies on the fact that the reactive precursors used for layer-by-layer deposition of the films are separated in space instead the separation in time in conventional ALD. This distinction in the mode of operation results in striking capabilities of S-ALD compared with conventional ALD, that includes: (i) continuous processing of macroscopic substrates, (ii) about two orders of magnitude faster deposition because no pump and purge dead times, and (iii) applicability of the ALD chemistry in (inert) atmospheric pressures.

(23) CNT Growth Considerations

(24) The use of CNT drawing methods to form CNT webs, or continuous CVD growth of millimeter long CNTs for attaining CNT mats (woven and non-woven), and yarns with macroscopic dimensions are important. CNT forests are grown while paying attention to the specific details following well-established methods and with a particular attention to synthesis parameters which are critical for attaining high density, aligned and long CNTs that comprise the CNT forests. This includes the selection of catalyst composition, thickness, and chemical potential adjusted by pre-treatment procedures. In addition, standard growth parameters such as time, temperature, pressure, flow rate, and source gases are taken into account for providing the optimal CNT forest substrates. For example, it was reported that Fe catalyst layer pre-treatment conditions are critical for attaining highly spinnable CNT forests (Zhang Y, et al., 2009, ACS Nano, 3 2157). and that ethylene (C.sub.2H.sub.4) is a preferred carbon source over acetylene (C.sub.2H.sub.2), for example, for attaining CNT forests used for CNT drawing and spinning, as well as additional preparation details (Jia J et al. 2011, Carbon, 49, 1333).

(25) The methods described herein may be generalized to various carbon-based materials that may be modified using ALD, MLD and ALD-MLD combinations.

(26) The use of ALD-MLD enables to tailor the deposition of the thin layer to the carbon material surface by combining oxide layers, organic layers, and oxide-organic hybrid layers. Additional control over nucleation of the thin film at the carbon material surface may be achieved by controlling the substrate temperature by local cooling and heating and by temperature gradients and temporal ramping. Examples of carbon based materials include single, double, multi-wall carbon nanotubes and carbon nanotube bundles. The carbon based materials may be in the form of aerogel, woven mats, non-woven mats, fibers, bundles, aggregates, and more.

(27) The properties of the carbon based materials that are affected by the thin films deposited from the vapor phase using ALD, MLD and ALD-MLD combinations include mechanical, electrical, thermal, wetting, surface roughness, chemical reactivity and more. Initial vapor phase processing, without solvent may be followed by wet chemical processing after the wetting properties were modified in the first stage of ALD/MLD vapor phase reaction

(28) The surface modified carbon materials can be used as-is or as precursors for composite materials, for example, to fabricate nanocomposite yarns should be generalized to carbon nanotube composites, carbon nanotube bundles composites, carbon fiber composites, carbon nanotube mats composites, carbon nanotube powders composites.

(29) Following the modification of the carbon based materials by vapor phase reactions further chemical treatments in solvents may be performed more effectively after the wetting properties were modified in the first stage of ALD/MLD vapor phase reaction.

(30) ALD/MLD application method may include conventional ALD reactor, fluidized bed rector, high pressure spatial ALD or other type of reactor.

Non-Limiting Examples of Embodiments

(31) While examples provided herein have been performed on CNT mats, identical procedures may be applied to other CNT macrostructures such as yarns, fibers, webs, carbon cloth, buckypaper and others.

(32) Examples and utilities may be divided into different groups:

(33) 1. Tuning mechanical properties of CNT macrostructures using ALD-MLD;

(34) 2. Tuning wetting properties of CNT macrostructures using ALD-MLD;

(35) 3. Introducing functional groups such as amine groups to CNT macrostructures by ALD-MLD.

(36) 4. Combining Ti—EG with CNT macrostructures for taking advantage of the molecular permeability and other properties.

(37) 5. Combining Ti—EG with CNT macrostructures for photocatlytic functions, by applying the ALD/MLD procedure, using e.g., TiCl.sub.4—EG (MLD) and TiCl.sub.4—H.sub.2O (ALD).

(38) As stated herein, the present invention provides vapor phase chemistries that yield organic-inorganic hybrid thin films, for example, metal oxide-organic hybrids that are combined with CNT webs and CNT mats (woven and non-woven) to form new classes of nanocomposite yarn materials by vapor phase deposition techniques. MLD permits the introduction of molecular components in the deposited films. These are then used as molecular functionalities with the aim of tailoring the interfacial properties, with well controlled coverage, thickness, composition, and stoichiometry.

(39) A non-limiting list of three classes of nanocomposite yarn materials that are prepared by applying A/MLD to the CNT web and to CNT mats (woven and non-woven) are exemplified in examples 1-3:

Example 1: Nanocomposite CNT Yarn Materials with Optimized Mechanical Properties

(40) Methods: vapor phase chemistry protocols were developed for depositing the yarn nanocomposite matrix components, producing highly uniform, conformal coatings of CNT web surfaces and CNT mats (woven and non-woven) with maximal surface coverage, thus maximizing the overall interaction while excluding covalent modification at the CNT structures.

(41) Results: CNT webs and CNT mats (woven and non-woven) with high surface density functionalities for intimate CNT-matrix binding. Such nanocomposite yarn materials are desired for numerous applications where the mechanical properties of the materials are important.

Example 2: Nanocomposite CNT Yarn Materials Coupled with Photocatalytic Matrix Layer

(42) Such materials are highly attractive for self-cleaning fabrics, including advanced membranes and numerous other applications.

Example 3: Nanocomposite Yarn Materials with Tailored Electronic Properties

(43) Methods: Nanocomposite CNT yarn materials were coupled to electro-active matrix deposited at the CNT web stage using ALD and MLD deposited conductive oxides.

(44) This allows the tailoring the electronic properties of CNT-nanocomposite yarns with desired electronic functionalities. Such nanocomposite yarn materials are desired for numerous applications such as anodes, batteries, and super capacitors.

Example 4: Continuous Synthesis of Nanocomposite Yarn Materials

(45) Methods: Based on the results of examples 1-3 a class of nanocomposite yarn materials was selected for integration with spatial ALD to yield continuous synthesis of nanocomposite yarn materials.

(46) This include low pressure ALD, atmospheric pressure spatial ALD. Initial vapor phase processing, without solvent may be followed by wet chemical processing after the wetting properties were modified in the first stage of ALD/MLD vapor phase reaction.

(47) This objective is achieved by continuous S-ALD processing coupled to CNT-webs and CNT mats (woven and non-woven) with controlled interface engineering, CNT alignment and dispersion within the deposited matrix. (high risk, high gain)

Example 5: Organic-Inorganic Hybrid Films

(48) Here, two prototypes of organic-inorganic hybrid films were developed, where molecular components (R) are embedded in the deposited films.

(49) Two modes (I and II) are exemplified:

(50) Mode I

(51) (I.a) MLD of -M-O—(R)—O—M-, as in hybrid organic-inorganic thin films, also called metalcones, such as titanium-ethylene glycol (for M=Ti and R═C.sub.2H.sub.4, Ti-EG). In addition, when Ti-EG films are annealed, oxygen deficient TiO.sub.2 oxide is formed by controlled combustion of the organic component, (R), embedded in the thin film. This gives an oxide with an adjustable electronic structure including shifting of band-edge positions and introduction of in-gap defect states that mediate efficient electron transfer.

(52) The inventors have successfully demonstrated the first application of MLD for the preparation of highly photoactive thin films. This means that the organic components introduced by MLD can either be used as a sacrificial component to control the oxide electronic properties, or as a structural component to attain uniform coverage of the CNT scaffold and additional functionalization of the CNT-hybrid materials.

(53) (I.b) Molecularly Permeable Films by MLD.

(54) The use of MLD for tailoring metal oxide (MO) thin films with controlled compositions, doping, electronic structure, and architectures was demonstrated. A key characteristics of the as-prepared Ti—EG films, and other metalcones is the film permeability that provides a versatile handle for additional functionality and varying the interface properties. The permeability of Ti—EG films was studied and compared with conventional TiO.sub.2 films (by ALD). Ti—EG films prepared by MLD and annealed result in thin oxide coatings that are pin-hole free, yet retain electronic communication between the solution and the underlying conductive electrode.

(55) These properties are considered when designing modified CNT webs and CNT mats (woven and non-woven) that is used as precursors for nanocomposite yarn materials for advanced membrane and battery applications that exhibits response triggered by either pH changes or the presence of cations in solutions

(56) (I.c) Doping of Ti—EG films with metal cations. Ti—EG films permeability can be used for adsorbing cations that function as dopants once the modified Ti—EG films are annealed. For example, Ti—EG films adsorbed with Ni and Fe were annealed at various temperatures and characterized. Band gap (BG) values were extracted using Tauc's equation for the undoped, Fe-doped, and Ni-doped films for a range of anneal temperatures. A monotonic BG narrowing is obtained for doped films annealed up to 750° C. with lowest BG values obtained for both Fe-, and Ni-doped Ti—EG of 2.74 and 2.70 eV, respectively. The facile doping of TiO.sub.2 was utilized for optimizing the protective layer band structure and improvement of the overall photocatalytic performance of the system.

(57) Mode II

(58) (II.a) Tandem A/MLD of —O—(Si—R)—O—(Ti)—O, where the molecular component R is directly attached to Si, having a Si—C bond (FIG. 2). The organic component is used here for tailoring the interfacial properties and for coupling the coated CNT surface, by introducing functional groups such as amine, protected amine, or other for covalent, or non-covalent interactions, and for designing the nanocomposite-matrix interactions. Another feature of the tandem A/MLD deposited films originate from the layered structure of Si- and Ti-phases. The silicon sub-oxide form, [SiO.sub.x] (with Si—C bond), is deposited over the titanium oxide phase in its stoichiometric form, [TiO.sub.2]. Upon thermal treatment under Argon the following internal rearrangement takes place: [SiO.sub.x]—[TiO.sub.2].fwdarw.[SiO.sub.2]—[TinO.sub.(2n−1)], where the latter phase is a conductive Magnéli phase (FIG. 3B). The introduction of the relatively labile Si—C carbon affects the kinetics of the phase transformations.

(59) In summary, this means that the tandem A/MLD of Si-, Ti-layers can be used as a vapour phase method to introduce amine and other surface functionalities at the CNT surface, or by additional thermal treatment yield conductive oxide phases that are known as useful anode materials for various applications.

(60) Optimization and Characterization of a Tandem A/MLD Growth Process for Ti—Si Oxide Nanocomposites Layers

(61) Linear film growth is demonstrated for various A/MLD process ratios and the respective growth per cycle (GPC) extracted from the thickness vs. cycle (FIG. 3A). The A/MLD films annealed under Argon yield conductive oxide layers, resulting in a facile transformation of the TiO.sub.2 to the conductive Magnéli phase. The transformation of TiO.sub.2 anatase and rutile phases in the films to conductive Magnéli phases is deduced by X-ray diffraction (GIXRD configuration) and Raman analysis (not shown).

(62) A strong dependence of the film conductivity on the specific annealing temperature conditions was found, depending upon the A/MLD n/m cycles ratio (FIG. 3C, 1050° C.). Study of the electronic properties of Ti—Si oxide nanocomposites films by transport measurements, UV-VIS optical absorption, and XPS measurements indicate the co-existence of metallic- and semi-conducting phases.

(63) Generalization of the Tandem A/MLD to other silane precursors.

(64) The tandem process is demonstrated for four types of silane precursors listed in FIGS. 4A and 4C with precursor exposure times in the range of 0.15-1.2 sec and precursor purge times in the range of 7-25 sec (FIG. 4B). The selected side groups provide free amine (NH.sub.2) and protected (NMe2, NEt2) amines Additionally, a non-functional silane (TMOS) also yield Ti—Si hybrid films, although with a lower growth per cycle (GPC) value owing to the lack of base-catalysis in the process. For TMOS the deposition is catalyzed by acid (HCl) evolved at the TiCl.sub.4-H.sub.2O sub-cycle.