Comparative study on structure and properties of titanium/silicon mono‐ and co‐doped amorphous carbon films deposited by mid‐frequency magnetron sputtering

The titanium/silicon mono‐ and co‐doped amorphous carbon films were deposited by mid‐frequency magnetron sputtering Ti target, Si target, and Ti80S20 alloy target, respectively. The effects of doped elements on the composition, surface morphology, microstructure, and mechanical and tribological properties of the films were investigated. The results reveal that the ratio of sp³ and sp² carbon bonds of the films is regulated between 0.28 and 0.62 by a combination of Ti and Si dopant. The addition of small amounts of silicon leads to an increase in sp³ bonds and disorder degree of the sp² carbon. The co‐doped film exhibits significantly superior friction performance than the mono‐doped films. The ultra‐low friction (μ < 0.01) was achieved under a load of 2 N in ambient air with 40% RH. By comparing to the mono‐and co‐doped films, it is thought that the sp³/sp² ratio of the films may play a key role for the superlow friction. Copyright © 2013 John Wiley & Sons, Ltd.     

A Series of Isolable Silanoic Thio‐, Seleno‐, and Telluroesters (LSi(X)OR) with Donor‐Supported SiX Double Bonds (L=β‐Diketiminate; X=S,Se, Te)

The first silicon analogues of carbonic (carboxylic) esters, the silanoic thio‐, seleno‐, and tellurosilylesters 3 (Si?S), 4 (Si?Se), and 5 (Si?Te), were prepared and isolated in crystalline form in high yield. These thermally robust compounds are easily accessible by direct reaction of the stable siloxysilylene L(Si:)OSi(H)L′ 2 (L=HC(CMe)₂[N(aryl)₂], L′=CH[(C?CH₂)‐CMe][N(aryl)]₂; aryl=2,6‐iPr₂C₆H₃) with the respective elemental chalcogen. The novel compounds were fully characterized by methods including multinuclear NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Owing to intramolecular N→Si donor–acceptor support of the Si?X moieties (X=S, Se, Te), these compounds have a classical valence‐bond N⁺–Si–X^? resonance betaine structure. At the same time, they also display a relatively strong nonclassical Si?X π‐bonding interaction between the chalcogen lone‐pair electrons (n_π donor orbitals) and two antibonding Si? N orbitals (σ*_π acceptor orbitals mainly located at silicon), which was shown by IR and UV/Vis spectroscopy. Accordingly, the Si?X bonds in the chalcogenoesters are 7.4 ( 3 ), 6.7 ( 4 ), and 6.9 % ( 5 ) shorter than the corresponding Si? X single bonds and, thus, only a little longer than those in electronically less disturbed Si?X systems (“heavier” ketones).     

Photodegradation of C‐PCPDTBT and Si‐PCPDTBT: Influence of the Bridging Atom on the Stability of a Low‐Band‐Gap Polymer for Solar Cell Application

The kinetics of photodegradation and the reactivity of different sites of the low‐band‐gap polymers poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (C‐PCPDTBT) and poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (Si‐PCPDTBT) are investigated as thin films and are compared to those of poly(3‐hexylthiophene) (P3HT). The decay kinetics are monitored with UV/Vis spectroscopy and the reactivity and product evolution are investigated with X‐ray photoelectron spectroscopy (XPS). Both polymers exhibit higher stability than P3HT. The bridging atom in the cyclopentadithiophene (CPDT) subunit has a significant influence on the stability. Varying oxidation rates for the different elements were observed. In the case of Si‐PCPDTBT, the silicon atom is oxidized primarily, whereas the photooxidation rates of the other elements are reduced relative to C‐PCPDTBT. Additionally, XPS experiments with varying excitation energies reveal a significant reaction gradient within a few nanometers of the surface of degraded thin films of C‐PCPDTBT.     

Silyl modification of biologically active compounds. 11. Synthesis,physico‐chemical and biological evaluation of N‐(trialkoxysilylalkyl)tetrahydro(iso,silaiso) quinoline derivatives

N‐(trialkoxysilylalkyl) derivatives of 1,2,3,4‐tetrahydroquinoline, 1,2,3,4‐tetrahydroisoquinoline and 4,4‐dimethyl‐4‐sila‐1,2,3,4‐tetrahydroisoquinoline were prepared and characterized by elemental analysis, ¹H, ¹³C and ²⁹Si NMR spectroscopy. In vivo psychotropic properties and in vitro cytotoxic effects of 3‐[N‐(1,2,3,4‐tetrahydroisoquinolyl)]propyltriethoxysilane methiodide and 3‐[N‐(1,2,3,4‐tetrahydroisoquinolyl)]propylsilatrane are reported. Comparative study of ²⁹Si shifts in newly synthesized compounds suggested donor–acceptor interaction between nitrogen and silicon atom, which increased electron density at Si nuclei, revealing a stronger increment of N → Si transannular bond in comparison with N → Si α‐effect. The molecular structure of 3‐[N‐(1,2,3,4‐tetrahydroisoquinolyl)]propylsilatrane features a penta‐coordinate silicon atom having CSiO₃ pattern and Si…N intramolecular interaction. Copyright © 2005 John Wiley & Sons, Ltd.     

Vacuum‐UV Irradiation‐Based Formation of Methyl‐Si‐O‐Si Networks from Poly(1,1‐Dimethylsilazane‐co‐1‐methylsilazane)

The vacuum‐UV (VUV)‐induced conversion of commercially available poly(1,1‐dimethylsilazane‐co‐1‐methylsilazane) into methyl‐Si‐O‐Si networks was studied using UV sources at wavelengths around 172, 185, and 222 nm, respectively. Time‐of‐flight secondary ion mass spectroscopy (TOF‐SIMS), X‐ray photo electron spectroscopy (XPS), and Fourier transform infrared (FTIR) measurements, as well as kinetic investigations, were carried out to elucidate the degradation process. First‐order kinetics were found for the photolytically induced decomposition of the Si? NH‐Si network, the subsequent formation of the methyl‐Si‐O‐Si network and the concomitant degradation of the Si? CH₃ bond, which were additionally independent of the photon energy above a threshold of about 5.5 eV (225 nm). The kinetics of these processes were, however, dependent on the dose actually absorbed by the layer and, in the case of Si‐O‐Si formation, additionally on the oxygen concentration. The release of ammonia and methane accompanied the conversion process. Quantum‐chemical calculations on methyl substituted cyclotetrasilazanes as model compounds substantiate the suggested reaction scheme. Layers <100 nm in thickness based on mixtures of poly(1,1‐dimethylsilazane‐co‐1‐methylsilazane) and perhydropolysilazane (PHPS) were coated onto polyethylene terephthalate (PET) foils by a continuous roll to roll process and cured by VUV irradiation by using wavelengths <200 nm and investigated for their O₂ and water vapor‐barrier properties. It was found that the resulting layers displayed oxygen and water vapor transmission rates (OTR and WVTR, respectively) of <1 cm³ m^?2 d^?1 bar^?1 and <4 g m^?2 d^?1, respectively.     

Synthesis,structure and biological activity of new 6,6‐dimethyl‐2‐oxo‐4‐{2‐[5‐organylsilyl(germyl)]furan(thiophen)‐2‐yl}vinyl‐5,6‐dihydro‐2H‐pyran‐3‐carbonitriles

New 6,6‐dimethyl‐2‐oxo‐4‐{2‐[5‐alkylsilyl(germyl)]furan(thiophen)‐2‐yl}vinyl‐5,6‐dihydro‐2H‐pyran‐3‐carbonitriles (IC₅₀: 1–6 µg ml^?1) have been prepared by the condensation of corresponding silicon‐ and germanium‐containing furyl(thienyl)‐2‐carbaldehydes with 3‐cyano‐4,6,6‐trimethyl‐5,6‐dihydropyran‐2‐one using piperidine acetate as a catalyst. The obtained carbonitriles were identified using NMR (¹H, ¹³C and ²⁹Si) spectroscopy and GC‐MS. The structure of 6,6‐dimethyl‐2‐oxo‐4‐[2‐(5‐trimethylsilyl)thiophen‐2‐yl]‐5,6‐dihydro‐2H‐pyran‐3‐carbonitrile was studied using X‐ray diffractometry. The influences of the heterocycle and the structure of the organoelement substituent on cytotoxicity and on matrix metalloproteinase inhibition have been studied. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of a‐Si (N+)/c‐Si (P) hetero‐junction solar cell through AFORS‐HET simulation

In this paper, a TCO/a‐Si(N⁺)/a‐Si(i)/c‐Si(P)/Al‐BSF(P⁺) structure hetero‐junction (HJ) cell model is developed. With AFORS‐HET V3.0, we investigate the influence of amorphous silicon (a‐Si) emitter and amorphous silicon (a‐Si)/crystalline silicon (c‐Si) interface defects on the HJ cell performance. Through modulating a‐Si(N⁺) emitter doping concentration and band offset at a‐Si/c‐Si interface, a maximum width value of 103 nm inversion layer is observed in the c‐Si(P) side. For 1 Ω.cm c‐Si (P) substrate, emitter doping of over 1 × 10²⁰ cm^?3 is necessary for achieving a high‐efficiency a‐Si/c‐Si HJ cell. Furthermore, defects at a‐Si(N⁺)/c‐Si(P) interface severely affect the open circuit voltage (Voc) and short circuit current density (Jsc) of the cell. Meanwhile, simulation indicates that Voc is more sensitive to interface defect density (Dit) than Jsc. A thin a‐Si(i) layer between a‐Si(N⁺) and c‐Si(P) does induce great improvement in Voc of TCO/a‐Si(N⁺)/a‐Si(i)/c‐Si(P)/Al‐BSF(P⁺) cell. As a result, high cell efficiency of 22.27% is achieved for a‐Si(N⁺)/c‐Si(P) HJ Cell with optimized parameters. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,Characterization, Thermal Property of Si(c‐C5H9NH)4 and Its Potential as CVD Precursor for SiC Film

Silicon(IV) amide Si(c‐C₅H₉NH)₄ ( 1 ), was synthesized and characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy, EI‐MS, elemental analysis, and X‐ray diffraction. Its thermal stability and volatility were also investigated. The as‐grown film, which was characterized by SEM, AFM, XRD and XPS, was deposited using 1 as single precursor through a low‐pressure chemical vapor deposition (LPCVD) process at a temperature as low as 600 °C. The results demonstrated that silicon(IV) amides can be promising single‐precursor for deposition of low‐temperature SiC films.     

Photocurrent Enhancement of Dye‐Sensitized Solar Cells owing to Increased Dye‐Adsorption onto Silicon‐Nanoparticle‐Coated Titanium‐Dioxide Films

The inverse‐micellar preparation of Si nanoparticles (Nps) was improved by utilizing sodium naphthalide. The Si Nps were subsequently functionalized with 4‐vinylbenzoic acid for their attachment onto TiO₂ films of dye‐sensitized solar cells (DSSCs). The average diameter of the COOH‐functionalized Si (Si? COOH) Nps was 4.6(±1.7) nm. Depth profiling by secondary‐ion mass spectrometry revealed that the Si Nps were uniformly attached onto the TiO₂ films. The number of Ru^II dye molecules adsorbed onto a TiO₂ film that was treated with the Si? COOH Nps was 42 % higher than that on the untreated TiO₂ film. As a result, DSSCs that incorporated the Si? COOH Nps exhibited higher short‐circuit photocurrent density and an overall energy‐conversion efficiency than the untreated DSSCs by 22 % and 27 %, respectively. This enhanced performance, mostly owing to the intramolecular charge‐transfer to TiO₂ from the dye molecules that were anchored to the Si? COOH Nps, was confirmed by comparing the performance with two different Ru^II–bipyridine dyes (N719 and N749).     

Synthesis and structure of novel spirosilanes. Combination of 1,2‐hydroboration and 1,1‐organoboration

The reaction of tetra(alkyn‐1‐yl)silanes Si(C?C‐R¹)₄ 1 [R¹ = ^tBu ( a ), Ph ( b ), C₆H₄‐4‐Me ( c )] with 9‐borabicyclo[3.3.1]nonane (9‐BBN) in a 1:2 ratio affords the spirosilane derivatives 5a – c as a result of twofold intermolecular 1,2‐hydroboration, followed by twofold intramolecular 1,1‐organoboration. Intermediates 3a–c , in which two alkenyl‐ and two alkyn‐1‐yl groups are linked to silicon, were identified by NMR spectroscopy. The molecular structure of the spiro compound 5c was determined by X‐ray analysis, and the solution‐state structures of products and intermediates follow conclusively from the consistent NMR spectroscopic data sets (¹H, ¹¹B, ¹³C and ²⁹Si NMR). Copyright © 2008 John Wiley & Sons, Ltd.     

Transition‐Metal‐Mediated Cleavage of Fluoro‐Silanes under Mild Conditions

Si?F bond cleavage of fluoro‐silanes was achieved by transition‐metal complexes under mild and neutral conditions. The Iridium‐hydride complex [Ir(H)(CO)(PPh₃)₃] was found to readily break the Si?F bond of the diphosphine‐ difluorosilane {(o‐Ph₂P)C₆H₄}₂Si(F)₂ to afford a silyl complex [{[o‐(iPh₂P)C₆H₄]₂(F)Si}Ir(CO)(PPh₃)] and HF. Density functional theory calculations disclose a reaction mechanism in which a hypervalent silicon species with a dative Ir→Si interaction plays a crucial role. The Ir→Si interaction changes the character of the H on the Ir from hydridic to protic, and makes the F on Si more anionic, leading to the formation of H^δ+???F^δ? interaction. Then the Si?F and Ir?H bonds are readily broken to afford the silyl complex and HF through σ‐bond metathesis. Furthermore, the analogous rhodium complex [Rh(H)(CO)(PPh₃)₃] was found to promote the cleavage of the Si?F bond of the triphosphine‐monofluorosilane {(o‐Ph₂P)C₆H₄}₃Si(F) even at ambient temperature.     

The high‐temperature tribological properties of Si‐DLC films

The tribological properties of Silicon‐containing diamond‐like‐carbon (Si‐DLC) films, deposited by magnetron sputtering Si target in methane/argon atmosphere, were studied in comparison with diamond‐like‐carbon (DLC) films. The DLC films disappeared because of the oxidation in the air at 500 °C, whereas the Si‐DLC films still remained, implying that the addition of Si improved significantly the thermal stability of DLC films. Retarded hydrogen release from DLC film at high temperature and silicon oxide on the surface might have contributed to lower friction coefficient of the Si‐DLC films both after annealing treatment and in situ high‐temperature environment. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis of 4‐silaspiro[3.4]octa‐1,5‐diene derivatives: hybrid spiro compounds

Trialkynyl(vinyl)silanes CH₂?CH? Si(C?C? R)₃ (R = Bu, Ph, p‐tolyl) were prepared and treated with 9‐borabicyclo[3.3.1]nonane (9‐BBN). Consecutive 1,2‐hydroboration and intramolecular 1,1‐carboboration reactions (each requires different reaction conditions) were studied. 1,2‐Hydroboration of the Si? vinyl group takes place at ambient temperature (23°C in tetrahydrofuran), followed by intramolecular 1,1‐vinylboration to give 1‐silacyclopent‐2‐ene derivatives, bearing still two alkynyl functions at the silicon atom. Further treatment with a second equivalent of 9‐BBN affords 1‐alkenyl‐1‐(alkynyl)‐1‐silacyclopent‐2‐ene derivatives. These undergo intramolecular 1,1‐vinylboration to give 4‐silaspiro[3.4]octa‐1,5‐dienes bearing the boryl groups at 2 and 6 positions. Protodeborylation of all new compounds (intermediates and final products) using acetic acid in slight excess afforded corresponding silanes including spirosilanes. All compounds were characterized using multinuclear NMR spectroscopy (¹H, ¹¹B, ¹³C, ²⁹Si) in solution state. Solid‐state structures for one of the trialkynyl(vinyl)silanes (R = p‐tolyl) and one of the 1‐silacyclopent‐2‐ene derivatives (R = Ph) were confirmed using X‐ray diffraction. Copyright © 2015 John Wiley & Sons, Ltd.     

Neutral Penta‐ and Hexacoordinate Silicon(IV) Complexes Containing Two Bidentate Ligands Derived from the α‐Amino Acids (S)‐Alanine, (S)‐Phenylalanine,and (S)‐tert‐Leucine

The neutral hexacoordinate silicon(IV) complex 6 (SiO₂N₄ skeleton) and the neutral pentacoordinate silicon(IV) complexes 7 – 11 (SiO₂N₂C skeletons) were synthesized from Si(NCO)₄ and RSi(NCO)₃ (R=Me, Ph), respectively. The compounds were structurally characterized by solid‐state NMR spectroscopy ( 6 – 11 ), solution NMR spectroscopy ( 6 and 10 ), and single‐crystal X‐ray diffraction ( 8 and 11 were studied as the solvates 8? CH₃CN and 11? C₅H₁₂ ? 0.5 CH₃CN, respectively). The silicon(IV) complexes 6 (octahedral Si‐coordination polyhedron) and 7 – 11 (trigonal‐bipyramidal Si‐coordination polyhedra) each contain two bidentate ligands derived from an α‐amino acid: (S)‐alanine, (S)‐phenylalanine, or (S)‐tert‐leucine. The deprotonated amino acids act as monoanionic ( 6 ) or as mono‐ and dianionic ligands ( 7 – 11 ). The experimental investigations were complemented by computational studies of the stereoisomers of 6 and 7 .     

The Family of Ferrocene‐Stabilized Silylium Ions: Synthesis, 29Si NMR Characterization,Lewis Acidity,Substituent Scrambling,and Quantum‐Chemical Analyses

The purpose of this systematic experimental and theoretical study is to deeply understand the unique bonding situation in ferrocene‐stabilized silylium ions as a function of the substituents at the silicon atom and to learn about the structure parameters that determine the ²⁹Si NMR chemical shift and electrophilicity of these strong Lewis acids. For this, ten new members of the family of ferrocene‐stabilized silicon cations were prepared by a hydride abstraction reaction from silanes with the trityl cation and characterized by multinuclear ¹H and ²⁹Si NMR spectroscopy. A closer look at the NMR spectra revealed that additional minor sets of signals were not impurities but silylium ions with substitution patterns different from that of the initially formed cation. Careful assignment of these signals furnished experimental proof that sterically less hindered silylium ions are capable of exchanging substituents with unreacted silane precursors. Density functional theory calculations provided mechanistic insight into that substituent transfer in which the migrating group is exchanged between two silicon fragments in a concerted process involving a ferrocene‐bridged intermediate. Moreover, the quantum‐chemical analysis of the ²⁹Si NMR chemical shifts revealed a linear relationship between δ(²⁹Si) values and the Fe???Si distance for subsets of silicon cations. An electron localization function and electron localizability indicator analysis shows a three‐center two‐electron bonding attractor between the iron, silicon, and C′_ipso atoms, clearly distinguishing the silicon cations from the corresponding carbenium ions and boranes. Correlations between ²⁹Si NMR chemical shifts and Lewis acidity, evaluated in terms of fluoride ion affinities, are seen only for subsets of silylium ions, sometimes with non‐intuitive trends, indicating a complicated interplay of steric and electronic effects on the degree of the Fe???Si interaction.     

Synthesis and properties of Q‐silicon crosslinked siloxane networks: H3PO4‐catalyzed sol–gel dehydration/crosslinking of α,ω‐bis(hydroxy)oligodimethylsiloxanes with tetrakis(hydroxydimethylsiloxy)silane

Six silicate‐crosslinked oligodimethylsiloxane thin films were prepared by the phosphoric acid (1 mol %) catalyzed condensation of α,ω‐bis(hydroxy)oligodimethylsiloxane (P) and tetrakis(hydroxydimethylsiloxy)silane (Q). Other acid catalysts were evaluated. P and Q were prepared by the Pd‐catalyzed oxidation of the corresponding Si? H compounds with water. The starting materials were characterized by IR and ¹H, ¹³C, and ²⁹Si NMR. A thermal cure was achieved with H₃PO₄ in 24 h and with poly(phosphoric acid) in 3 h at 110–120 °C. Dynamic mechanical analysis was used to determine the glass‐transition temperatures and to evaluate the mechanical properties of the films. Their thermal stabilities (≥300 °C) in air and N₂ were determined by thermogravimetric analysis. Small amounts of non‐crosslinked P were recovered from the films by Soxhlet extractions with CH₂Cl₂ and analyzed by IR, gel permeation chromatography, and ²⁹Si NMR. The crosslink densities were evaluated by the CH₂Cl₂ absorption capacities of the films. The surface properties of the films were determined by static and dynamic contact‐angle measurements. Electrochemical impedance spectroscopy was carried out to evaluate the corrosion‐protective properties of the coatings on mild steel as a function of the exposure time to 0.5 N NaCl. The biofoul‐release properties of the films were evaluated with sporelings from mature Ulva linza plants and barnacles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2237–2247, 2006     

Zintl Clusters as Wet‐Chemical Precursors for Germanium Nanomorphologies with Tunable Composition

[Ge₉]^4? Zintl clusters are used as soluble germanium source for a bottom–up fabrication of Ge nanomorphologies such as inverse opal structures with tunable composition. The method is based on the assembly and oxidation of [Ge₉]^4? clusters in a template mold using SiCl₄, GeCl₄, and PCl₃ leading to Si and P‐containing Ge phases as shown by X‐ray diffraction, Raman spectroscopy, and energy‐dispersive X‐ray analysis. [Ge₉]^4? clusters are retained using ethylenediamine (en) as a transfer medium to a mold after removal of the solvent if water is thoroughly excluded, but are oxidized to amorphous Ge in presence of water traces. ¹H NMR spectroscopy reveals the oxidative deprotonation of en by [Ge₉]^4?. Subsequent annealing leads to crystalline Ge. As an example for wet‐chemical synthesis of complex Ge nanomorphologies, we describe the fabrication of undoped and P‐doped inverse opal‐structured Ge films with a rather low oxygen contents. The morphology of the films with regular volume porosity is characterized by SEM, TEM, and grazing incidence small‐angle X‐ray scattering.     

Reactivity of Extra‐framework Species of USY Zeolites in Alkaline Medium

Zeolites of type USY (ultra‐stable Y) were obtained by steaming of NH₄NaY modification. Samples were modified by subsequent alkaline treatment in KOH solution. USY and USY‐KOH were characterised by chemical element analysis, XRD, IR, ²⁹Al and ²⁹Si MAS NMR spectroscopic measurements. Correct silicon to aluminium ratios (Si/Al) were determined by XRD and IR (double ring vibration w_DR) data whereas values calculated according to data of ²⁹Si MAS NMR and IR spectroscopy (asymmetrical TOT valence vibration w_TOT) appeared to be too high., In the latter case, the signals of the zeolite framework were strongly superimposed by that of extra‐framework silica gel (EFSi) formed during steaming. It was found that alkaline leaching induces desilication of silicon‐rich area of the zeolite framework and partial dissolution of EFSi. Silicate ions of both react with likewise dissolved extra‐framework aluminium (EFAl) to form X‐ray amorphous aluminosilicate. Consequently, the superposition of the ²⁹Si MAS NMR signals of the zeolite framework by silica gel was reduced for Q⁴(0Al) but increased for Q⁴ (2Al) and Q⁴(3Al) structure units. A reinsertion of EFAl into the zeolite framework has not been observed.     

100 keV H+ ion irradiation of as‐deposited Al‐doped ZnO thin films: An interest in tailoring surface morphology for sensor applications

We report the influence of 100 keV H⁺ ion beam irradiation on the surface morphology, crystalline structure, and transport properties of as‐deposited Al‐doped ZnO (Al:ZnO) thin films. The films were deposited on silicon (Si) substrate by using DC sputtering technique. The ion irradiation was carried out at various fluences ranging from 1.0 × 10¹² to 3.0 × 10¹⁴ ions/cm². The virgin and ion‐irradiated films were characterized by X‐ray diffraction, Raman spectroscopy, atomic force microscopy, and Hall probe measurements. Using X‐ray diffraction spectra, 5 points Williamson‐Hall plots were drawn to deduce the crystallite site and strain in Al:ZnO films. The analysis of the measurements shows that the films are almost radiation resistant in the structural deformation under chosen irradiation conditions. With beam irradiation, the transport properties of the films are also preserved (do not vary orders of magnitude). However, the surface roughness and the crystallite size, which are crucial parameters of the ZnO film as a gas sensor, are at variation with the ion fluence. As ion fluence increases, the root‐mean‐square surface roughness oscillates and the surface undergoes for smoothening with irradiation at chosen highest fluence. The crystallite size decreases initially, increases for intermediate fluences, and drops almost to the value of the pristine film at highest fluence. In the paper, these interesting experimental results are discussed in correlations with ion‐matter interactions especially energy losses by the ion beam in the material.     

Thickness and temperature‐dependent study of Co/Si interface

Thin films of cobalt (10, 40, and 100 nm) are deposited on Si substrate by electron beam physical vapor deposition technique. After deposition, 4 pieces from each of the wafers of silicon substrate were cut and annealed at a temperature of 200°C, 300°C, and 400°C for 2 hours each, separately. X‐ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) are used to study the structural and morphological characteristics of the deposited films. To obtain TEM images, Co films are deposited on Cu grids; so far, no such types of TEM images of Co films are reported. Structural studies confirm nanocrystalline nature with hexagonal close packed structure of the deposited Co film at lower thickness, while at higher thickness, film structure transforms to amorphous with lower surface roughness value. The particle sizes in all the cases are in the range of 3 to 5 nm. Micro‐Raman spectroscopy is also used to study the phase formation and chemical composition as a function of thickness and temperature. The results confirm that the grown films are of good quality and free from any impurity. Studies show the silicide formation at the interface during deposition. The appearance of new band at 1550 cm⁻¹ as a result of annealing indicates the structural transformation from CoSi to CoSi₂, which further enhances at higher annealing temperatures.