Structural and electrical properties of ternary Ru–AlN thin films prepared by plasma-enhanced atomic layer deposition

Ruthenium–aluminum-nitride (Ru–AlN) thin films were grown by plasma-enhanced atomic layer deposition (PEALD) at 300 °C. The Ru intermixing ratio of Ru–AlN thin films was controlled by the number of Ru unit cycles, while the number of AlN unit cycles was fixed to one cycle. The electrical resistivity of Ru–AlN thin film decreased with increasing the Ru intermixing ratio, but a drastic decrease in electrical resistivity was observed when the Ru intermixing ratio was around 0.58–0.78. Bright-field scanning transmission electron microscope (BF-STEM) and energy-dispersive X-ray spectroscopy (EDX) element mapping analysis revealed that the electrical resistivity of Ru–AlN thin film was strongly dependent on the microstructures as well as on the Ru intermixing ratio. Although the electrical resistivity of Ru–AlN thin films decreased with increasing the Ru intermixing ratio, a drastic decrease in electrical resistivity occurred where the electrical paths formed as a result of the coalescence of Ru nanocrystals.     

Optical and electrical properties of E-Beam deposited TiO<Subscript>2</Subscript>/Si thin films

In this paper, optical and electrical properties of E-Beam deposited TiO₂/Si thin films have been studied and investigated extensively. The films were deposited on p-type (100) silicon wafer by using electron beam evaporation technique. The thickness of the thin films was measured by a spectroscopic reflectometer, which is about 216 nm. The fabricated titanium oxide (TiO₂) thin films were annealed at 800 °C for 1 h under N₂ ambient. X-ray diffraction measurements were performed to study the structure and phase identification of the fabricated TiO₂ thin films. For the optical properties, reflection, transmittance, refractive index and absorption coefficient were obtained and analyzed. The photocurrent and dark current of the fabricated films were measured by I–V measurements. The measurement of the current–voltage (I–V) characteristics possesses good ohmic contact. The electrical characterizations of the films were performed in the range of the low frequencies (50 and 100 kHz) and high frequencies (750 kHz and 1 MHz) by the capacitance–voltage and conductance–voltage measurements at room temperature. The capacitance of the fabricated TiO₂ MOS capacitor at both high and low frequencies increases with the decrease in frequencies. The obtained conductance curves (peaks) increase with the decreasing in the frequencies. This can be due to the interface state density, series resistance and interfacial dielectric of the fabricated MOS capacitors. The variation in the characteristics of the fabricated film shows that TiO₂ is a promising candidate to be used in the optoelectronic and future UV detector applications as a switch, such as an optical amplifier, emitter, and UV light detectors.     

Metal/nonpolar <Emphasis Type="Italic">m</Emphasis>-plane ZnO contacts with and without thin Al<Subscript>2</Subscript>O<Subscript>3</Subscript> interlayer deposited by atomic layer deposition

Using the temperature dependent current–voltage (I–V) measurements, the electrical properties of Au/nonpolar m-plane ZnO Schottky diodes with an Al₂O₃ interlayer prepared by atomic layer deposition (ALD) was investigated. With an Al₂O₃ interlayer, it was found to have higher barrier heights and higher rectifying ratio. Modified Richardson plots produced effective Richardson constants of 30.0 and 37.6 Acm^?2K^?2 for the samples with and without Al₂O₃ interlayer, respectively, which are similar to the theoretical value of 32.0 Acm^??2K^??2 for n-ZnO. Scanning transmission electron microscope (STEM) results showed that the oxygen-contained layer on ZnO surface degraded the film quality of subsequently deposited Al₂O₃ layer. In addition, the inter-diffusion of Au and Al atoms into ZnO subsurface region also modulated the electrical properties of Au/ZnO contacts.     

Optical and electrical properties of obliquely deposited a-GeSe<Subscript>2</Subscript> films

Oblique deposition and exposure to photons of energy greater than the bandgap have a marked effect on the structure and consequently on electrical and optical properties of amorphous chalcogenides. This paper presents a detailed study of photoinduced effect and oblique deposition effect on electrical and optical properties of a-GeSe₂ films deposited at different angles (0°–80°). The indirect-optical bandgap energy (2.18 eV) was found to be independent of angle of incidence. The spectral response of refractive index and extinction coefficient has been determined in the wavelength range of 0.6–1 μm using the transmission spectra. Refractive index decreases with the increase in angle of incidence. The value of refractive index was observed to be 2.28 for 0° and 2.00 for 80° films at 0.646 μm. An increase in bandgap was also observed on exposure to the UV light for ∼120 min. The change in bandgap became more significant with the increase in angle of incidence (∼ 2.3% for 0° and ∼10.6% for 80°). The temperature dependence of conductivity along with time dependence and spectral response of photocurrent has also been investigated.     

Micro-Raman spectroscopy and X-ray diffraction studies of atomic-layer-deposited ZrO<Subscript>2</Subscript> and HfO<Subscript>2</Subscript> thin films

Raman spectroscopy and X-ray diffraction (XRD) methods were applied to characterize ZrO₂ and HfO₂ films grown by atomic layer deposition (ALD) on silicon substrates in chloride- based processes. A dramatic enhancement in spectral quality of Raman data resulted from the use of the film’s freestanding edges for experimental runs between 80 and 800 cm⁻¹. Both techniques detected a preferential formation of a metastable phase in ZrO₂ and HfO₂ films at 500 and 600^∘C, respectively, during the initial stages of ALD. In the case of ZrO₂ films this phase was identified as the tetragonal polymorph of ZrO₂ (t-ZrO₂). XRD and Raman spectroscopy data showed that, in contrast to the monoclinic phase (m-ZrO₂), the absolute amount of t-ZrO₂ remained approximately constant while its relative amount decreased with the increase of the film thickness from 56 to 660 nm. Neither XRD nor Raman spectroscopy allowed unambiguous identification of the metastable phase formed in otherwise monoclinic HfO₂ films.     

Fabrication of SiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> double layer thin films with self-cleaning and photocatalytic properties

Transparent antireflective SiO₂/TiO₂ double layer thin films were prepared using a sol–gel method and deposited on glass substrate by spin coating technique. Thin films were characterized using XRD, FE-SEM, AFM, UV–Vis spectroscopy and water contact angle measurements. XRD analysis reveals that the existence of pure anatase phase TiO₂ crystallites in the thin films. FE-SEM analysis confirms the homogeneous dispersion of TiO₂ on SiO₂ layer. Water contact angle on the thin films was measured by a contact angle analyzer under UV light irradiation. The photocatalytic performance of the TiO₂ and SiO₂/TiO₂ thin films was studied by the degradation of methylene blue under UV irradiation. The effect of an intermediate SiO₂ layer on the photocatalytic performance of TiO₂ thin films was examined. SiO₂/TiO₂ double layer thin films showed enhanced photocatalytic activity towards methylene blue dye.     

Growth of aluminum nitride thin films prepared by plasma-enhanced atomic layer deposition

Aluminum nitride (AlN) thin films were deposited by atomic layer deposition from aluminum chloride (AlCl₃) and an ammonia/hydrogen plasma. The most important role of the ammonia/hydrogen plasma was to act as a reducing agent to extract Cl from AlCl₃, and to form AlN subsequently. The growth rate was saturated at ∼0.042 nm/cycle, and the thickness was proportional to the number of reaction cycles. Repeating this reaction cycle led to precisely controlled growth. The film properties were analyzed using Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy and time-of-flight elastic recoil detection analysis. The concentration of chlorine and hydrogen impurities was 0.23 and 2.01 at.%, respectively. AlN films showed good anti-oxidation properties when O₂ was annealed at 650 °C for 30 min.     

Coaxial multi-interface hollow Ni-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZnO nanowires tailored by atomic layer deposition for selective-frequency absorptions

In this work atomic layer deposition (ALD) was employed to fabricate coaxial multi-interface hollow Ni-Al2O3-ZnO nanowires.The morphology,microstructure,and ZnO shell thickness dependent electromagnetic and microwave absorbing properties of these Ni-A12O3-ZnO nanowires were characterized.Excellent microwave absorbing properties with a minimum reflection loss (RL) of approximately-50 dB at 9.44 GHz were found for the Ni-Al2O3-100ZnO nanowires,which was 10 times of Ni-A12O3 nanowires.The microwave absorption frequency could be effectively varied by simply adjusting the number of ZnO deposition cycles.The absorption peaks of Ni-Al2O3-100ZnO and Ni-A12O3-150ZnO nanowires shifted of 5.5 and 6.8 GHz towards lower frequencies,respectively,occupying one third of the investigated frequency band.The enhanced microwave absorption arose from multiple loss mechanisms caused by the unique coaxial multi-interface structure,such as multi-interfacial polarization relaxation,natural and exchange resonances,as well as multiple internal reflections and scattering.These results demonstrate that the ALD method can be used to realize tailored nanoscale structures,making it a highly promising method for obtaining high-efficiency microwave absorbers,and opening a potentially novel route for frequency adjustment and microwave imaging fields.     

Characteristics of nanocomposite ZrO2/Al2O3 films deposited by plasma-enhanced atomic layer deposition

Nanocomposite ZrO2/Al2O3 (ZAO) films were deposited on Si by plasma-enhanced atomic layer deposition and the film characteristics including interfacial oxide formation, dielectric constant (k), and electrical breakdown strength were investigated without post-annealing process. In both the mixed and nano-laminated ZAO films, the thickness of the interfacial oxide layer (T(IL)) was considerably reduced compared to ZrO2 and Al2O3 films. The T(IL) was 0.8 nm in nano-composite films prepared at a mixing ratio (ZrO2:Al2O3) of 1:1. The breakdown strength and the leakage current level were greatly improved by adding Al2O3 as little as 7.9% compared to that of ZrO2 and were enhanced more with increasing content of Al2O3. The k of ZrO2 and mixed ZAO (Al2O3 7.9%) films were 20.0 and 16.5, respectively. These results indicate that the addition of Al2O3 to ZrO2 greatly improves the electrical properties with less cost of k compared to the addition of SiO2.     

Structural,optical and microscopic properties of chemically deposited In<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films

Solar cell technologically important binary indium selenide thin film has been developed by relatively simple chemical method. The reaction between indium chloride, tartaric acid, hydrazine hydrate and sodium selenosulphate in an aqueous alkaline medium at room temperature gives deposits In₂Se₃ thin film. Various preparative parameters are discussed. The as grown films were found to be transparent, uniform, well adherent, red in color. The prepared films were studied using X-ray diffraction, scanning electron microscopy, atomic absorption spectroscopy, Energy dispersive atomic X-ray diffraction, optical absorption and electrical conductivity properties. The direct optical band gap value E_g for the films was found to be as the order of 2.35 eV at room temperature and having specific electrical conductivity of the order of 10⁻² (Ω cm)⁻¹ showing n-type conduction mechanism. The utility of the adapted technique is discussed from the point of view of applications considering the optoelectric and structural data obtained.     

Structural and surface morphological properties of chemically deposited Mo<Subscript>0.5</Subscript>W<Subscript>0.5</Subscript>S<Subscript>2</Subscript> thin film

Preparation of layered type semiconductor Mo_0.5W_0.5S₂ ⁻ thin films has been successfully done by using chemical bath deposition method. Objective of the studies are related to structural, optical, morphological and electrical properties of the thin films. The preparation method is based on the reaction between tartarate complex of Mo and W with thiourea in an aqueous alkaline medium at 363 K. X-Ray diffraction reveals a polycrystalline film composed of both MoS₂ and WS₂ phases. The optical study shows that the band gap of the film is 1.6 eV. Electrical conductivity is high which is in the order of 10⁻³–10⁻² (Ώ cm)⁻¹.     

Improved oxygen diffusion barrier properties of ruthenium-titanium nitride thin films prepared by plasma-enhanced atomic layer deposition

Ru-TiN thin films were prepared from bis(ethylcyclopentadienyl)ruthenium and tetrakis(dimethylamino)titanium using plasma-enhanced atomic layer deposition (PEALD). The Ru and TiN were deposited sequentially to intermix TiN with Ru. The composition of Ru-TiN films was controlled precisely by changing the number of deposition cycles allocated to Ru, while fixing the number of deposition cycles allocated to TiN. Although both Ru and TiN thin films have a polycrystalline structure, the microstructure of the Ru-TiN films changed from a TiN-like polycrystalline structure to a nanocrystalline on increasing the Ru intermixing ratio. Moreover, the electrical resistivity of the Ru0.67-TiN0.33 thin films is sufficiently low at 190 microomega x cm and was maintained even after O2 annealing at 750 degrees C. Therefore, Ru-TiN thin films can be utilized as a oxygen diffusion barrier material for future dynamic (DRAM) and ferroelectric (FeRAM) random access memory capacitors.     

Structural,optical, and electrical properties of In<Subscript>2</Subscript>S<Subscript>3</Subscript>:Sn thin films grown by chemical bath deposition on Pyrex

Sn-doped In₂S₃ thin films are deposited on Pyrex. Tin is incorporated in the solution using SnCl₂·2H₂O. The properties of the films are investigated by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, spectrophotometry, and thermally stimulated current (TSC) measurements. XRD analysis reveals that the films become almost amorphous when tin exceeds well determined optimum quantity. The investigation of optical properties shows that the band gap depends on the value of the Sn concentration. It is also observed that upon adding the optimum quantity of tin, the maximum of the TSC intensity increased by 2 orders of magnitude. These results are discussed with respect to introduce the effect of tin incorporated in the physical properties.     

Induced NH<Subscript>2</Subscript> bonding of carbon nanotubes using NH<Subscript>3</Subscript> plasma-enhanced chemical vapor deposition

Plasma-enhanced chemical vapor deposition was used to modify the multiwall carbon nanotubes (MWCNTs) using ammonia (NH₃) plasma. For various durations of NH₃ plasma treatment, a scanning electron microscope, X-ray, Raman spectroscopy and contact angle measurement were used to ascertain several characteristics of the MWCNTs. The experimental results show that: (1) the length of the MWCNTs is reduced, if the duration of the plasma treatment is increased; (2) the NH₃ plasma treatment can incorporate amine (NH₂ ⁻) or amino (NH⁻) functional groups onto the MWCNT surface; (3) the plasma treated carbon nanotubes become more hydrophilic.     

Preparation and Properties of Thin HfO<Subscript>2</Subscript> Films

HfO₂ layers were grown on silicon by metalorganic chemical vapor deposition using (C₅H₅)₂Hf(CH₃)₂, (C₅H₅)₂Hf(N(C₂H₅)₂)₂, and Hf(dpm)₄ as volatile precursors and were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, and IR spectroscopy. The films were shown to consist of monoclinic HfO₂ and to contain hafnium silicide and silicate at the HfO₂/Si interface. The presence of hafnium silicide was attributed to oxygen deficiency produced by argon ion milling. Hafnium silicate was formed as a result of the reaction between hafnium and silicon oxides during annealing. Current-voltage and capacitance-voltage measurements on Al/HfO₂/Si test structures were used to determine the dielectric permittivity and electrical resistivity of the films: ? = 15–20, ρ ～ 10¹⁵ cm.     

Self-limiting low-temperature growth of crystalline AlN thin films by plasma-enhanced atomic layer deposition

We report on the self-limiting growth and characterization of aluminum nitride (AlN) thin films. AlN films were deposited by plasma-enhanced atomic layer deposition on various substrates using trimethylaluminum (TMA) and ammonia (NH₃). At 185 °C, deposition rate saturated for TMA and NH₃ doses starting from 0.05 and 40 s, respectively. Saturative surface reactions between TMA and NH₃ resulted in a constant growth rate of ~ 0.86 Å/cycle from 100 to 200 °C. Within this temperature range, film thickness increased linearly with the number of deposition cycles. At higher temperatures (≥ 225 °C) deposition rate increased with temperature. Chemical composition and bonding states of the films deposited at 185 °C were investigated by X-ray photoelectron spectroscopy. High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.02 and 396.07 eV, respectively. Films deposited at 185 °C were polycrystalline with a hexagonal wurtzite structure regardless of the substrate selection as determined by grazing incidence X-ray diffraction. High-resolution transmission electron microscopy images of the AlN thin films deposited on Si (100) and glass substrates revealed a microstructure consisting of nanometer sized crystallites. Films exhibited an optical band edge at ~ 5.8 eV and an optical transmittance of > 95% in the visible region of the spectrum.     

Structural,optical and microscopic properties of chemically deposited Mo<Subscript>0.5</Subscript>W<Subscript>0.5</Subscript>Se<Subscript>2</Subscript> thin films

Mo_0.5W_0.5Se₂ thin films were obtained by using relative simple chemical route at room temperature. Various preparative conditions of the thin films are outlined. The films were characterized by X-ray diffraction, scanning electron microscope, optical and electrical properties. The grown films were found to be uniform, well adherent to substrate and brown in color. The X-ray diffraction pattern shows that thin films have a hexagonal phase. Optical properties show a direct band gap nature with band gap energy 1.44 eV and having specific electrical conductivity in the order of 10⁻⁵ (Ωcm)⁻¹.     

Photoelectrochemical applications of In<Subscript>2</Subscript>Se<Subscript>3</Subscript> thin films by chemical deposition

Indium selenide films have been synthesized by chemical bath deposition method onto stainless steel plate. The configuration of fabricated cell is n-In₂Se₃| NaOH(1 M) + S(1 M) + Na₂S(1 M) |C_(graphite). Characterization of the photoelectrochemical cell was carried out by studying X-ray diffraction, current–voltage and capacitance–voltage characteristics in the dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that the In₂Se₃ thin films are n-type semiconductor. The junction ideality factor was found to be 3.24. The flat band potential and the barrier height were found to be 0.720 V and 0.196 eV, respectively. From the study of power output characteristics, open circuit voltage, short circuit current, fill factor and efficiency were found to be 310 mV, 20 μA, 37.64 and 0.61%, respectively. Photoresponse studies show that the lighted ideality factor is 2.78. Maximum current was observed at 575 nm.