Resistivity Of Thin Films Research Articles

Enhancement of electrical and photo-electrical properties of P3HT:CrCl2 thin films for photo sensing applications

In this work, doped and undoped P3HT thin films are prepared and deposited onto ITO interdigitated electrodes. To improve the optical and the electrical properties of the pure P3HT thin film, chromium(II) chloride was used as dopant material with three different weight percentage, 2.5%, 5%, 10%. Room-temperature current–voltage (I-V) characteristics of the samples were measured, showing an increase in the electrical current with increasing the dopant concentration. Under dark condition, the conductivity and resistivity of the pure P3HT thin films were enhanced by a factor of 5× as a result of doping the P3HT by 10 wt% of CrCl2. Under light intensity (50 mW cm−2) and at 10 V bias, the conductivity and resistivity obtained from P3HT:CrCl2 (10 wt%) thin films are 4.75 × 10−4 S cm−1 and ∼2 kΩ, respectively. These results exhibit an enhancement by a factor of ∼12× compared to those obtained from pure P3HT thin film. The current of the photo-sensors based on doped/undoped P3HT thin films are measured as a function of time under light intensity ranging from 0 to 50 mW cm−2 at 1 V bias, exhibiting high photo-response and good reproducibility. Three different wavelengths, white, green, and red were used as light sources to expose the photo-sensors. Under white light, photo-sensor based on P3HT:CrCl2(10 wt%) exhibit the highest values of the photo-responsivity and quantum efficiency, ∼23.3 mA W−1 and 5.8%, respectively, showing an enhancement by a factor of ∼ 11.5× compared to those obtained from the photo-sensor based on pure P3HT.

Heterogeneous Integration of Acoustic Microextraction with an Optoelectronic Sensor on Glass for Nucleic Acid Testing.

Lab-on-a-chip systems (LOCs), characterized by their high sensitivity, low sample consumption, and portability, have significantly advanced the field of on-site testing. Despite the evolution of integrated LOCs from qualitative to quantitative analyses, on-chip full integration of sample preparation, purification, and multiplexed detection remains a challenge. Here, we propose a strategy for the heterogeneous integration of a set of complementary metal oxide semiconductor-compatible devices including acoustic resonator, thin-film resistors, and temperature/photosensors as a new type of LOC for nucleic acid testing (NAT). Programmed acoustic streaming-based particles and fluid manipulations largely simplify the nucleic acid extraction process including cell lysis, nucleic acid capture, and elution. The design of the acoustic microextraction module and extraction process was thoroughly studied. Benefitted by the microelectromechanical system approach, the conventional mechanical actions and complex flow control are avoided, which enables a compact hand-held NAT instrument without complicated peripherals. Validation experiments conducted on plasma-harboring mutations in the epidermal growth factor receptor (EGFR) gene confirmed the robustness of the system, achieving an impressive nucleic acid (NA) extraction efficiency of approximately 90% within 5 min and a limit of detection of the target NA in the plasma of 1 copy/μL.

Simultaneous determination of the phase boundary thermal resistance and thermal conductivity in phase-separated TiO2 thin films

Phase boundaries, most often between crystalline and amorphous phases of a material, are ubiquitous lattice imperfections in thin films, particularly deposited by low temperature processes such as atomic layer deposition (ALD). Thermal resistances from these boundaries may impede phonon transport and reduce thermal conductivity. However, to date, there have been no reports on the direct measurement of the phase boundary thermal resistance, due in part to challenges associated with fabricating an atomically flat yet geometrically planar interface between different phases within a film. Here, we present a systematic study to simultaneously determine the phase boundary thermal resistance and thermal conductivity in a series of phase-separated titanium oxide (TiO2) thin films prepared via plasma-enhanced ALD (PEALD). A precise implementation of per-cycle plasma treatment enables extremely localized crystallization—i.e., plasma-assisted atomic layer annealing (ALA)—and the fabrication of crystalline/amorphous layered structures with their respective thicknesses systematically varied. Frequency-domain thermoreflectance measures the effective thermal conductivity of each film and its top and bottom interfaces, confirmed independently using time-domain thermoreflectance. We simultaneously solve a system of linear equations generated by applying a series resistor model to each film, yielding the phase boundary thermal resistance of 5.1 m2 K GW–1 between crystalline and amorphous TiO2, as well as the thermal conductivities of 5.1 and 2.1 W m–1 K–1 for crystalline and amorphous TiO2, respectively. The results suggest that the crystalline/amorphous phase boundary acts like a layer of crystalline (amorphous) TiO2 with equivalent thickness ∼26 (∼11) nm.

Effect of vacuum-ultraviolet irradiation on structure and resistivity of epitaxial copper oxide thin films

Effect of vacuum-ultraviolet irradiation on structure and resistivity of epitaxial copper oxide thin films

Low-resistivity molybdenum-carbide thin films formed by thermal atomic layer deposition with pressure-assisted decomposition reaction

The rapid increase in the resistivity of thin metal films as their thickness decreases to sub-10 nm, known as the resistivity size effect, is an important issue that must be addressed to ensure device performance in ultraminiaturized semiconductor devices. Molybdenum carbide (MoCx) has been studied as a candidate for emerging interconnection materials because it can maintain a low resistivity even at a low thickness. However, reports on stable precursors with guaranteed reactivity for atomic layer deposition (ALD) remain limited; moreover, the process of forming low-resistance MoCx thin films must be studied. In this study, we propose a new route to form low-resistivity MoCx thin films by thermal ALD with partial ligand dissociation by controlling the process pressure to enhance the reactivity of the Mo precursor with reactants. Following the proposed deposition process and subsequent annealing, uniform and continuous thin films were formed (even at a sub-5 nm thickness), with an extremely low resistivity of approximately 130 μΩ cm. Therefore, the proposed method can be applied as a next-generation interconnect process; notably, high-quality thin films can be formed through pressure-assisted decomposition, even with a lack of thermal energy during the ALD process.

Understanding interfacial compounds induced by Ag diffusion on improving interface electrical contact resistivity between the Cu electrode and Bi2Te3 thin film

It has been reported that introducing Ag interlayer at the Cu/Bi2Te3 interface can achieve ultra-low electrical contact resistivity. However, there is no consensus on the influence of Ag diffusion induced by Ag interlayer on electrical contact. Thus, the impact of Ag diffusion on electrical contact conductivity for Cu/Ag/Bi2Te3 multilayers was investigated. The generation of interfacial compounds induced by Ag diffusion was analyzed and the contact resistivity was measured in Cu/Ag/Bi2Te3 multilayers with different Ag interlayer thickness before and after annealing. It was found that Ag diffusion induced interfacial compounds Cu4Ag3Te4 at the Cu/Ag interface before annealing, which could decrease contact resistivity to 3.728×10−12 Ω∙m2. After annealing, the relative amount of Cu4Ag3Te4 at the Cu/Ag interface slightly decreased, and the Ag2Te was found to appear at the Ag/Bi2Te3 interface, which could further decrease contact resistivity to 3.187×10−12 Ω∙m2. With Ag interlayer thickness increasing from 50 nm to 300 nm, the contact resistivity decreased from 3.726×10−10 Ω∙m2 to 3.728×10−12 Ω∙m2 before annealing because the relative amount of Cu4Ag3Te4 increased about 5 times, after annealing the contact resistivity further decreased by 10.27∼41.7 % because the relative amount of Ag2Te increased about 1.1 times. In addition, we had optimized the ultra-low contact resistivity test method by redesigning the structure of test samples and modifying the formula of contact resistivity to eliminate two errors. One is caused by Cu electrode short-circuit resistance due to the test current being short-circuited by the middle electrode between two test electrodes. The other is caused by the increased electrical resistance of Bi2Te3 thin film due to Te atom volatilization after annealing. The results showed that the errors of the test results were reduced by at least 21.50 %. Our work provides guidance for further optimizing electrical contact of thin-film thermoelectric devices.

The Effect of Deposition Temperature on TiN Thin Films for the Electrode Layer of 3D Capacitors Prepared by Atomic Layer Deposition

The TiN thin film is considered a promising electrode layer for 3D capacitors. In this study, TiN thin films were prepared on Si substrates using atomic layer deposition (ALD) at various temperatures from 375 °C to 475 °C. The crystallization behavior, microstructure, and conductance properties of those TiN thin films were investigated. The resistivity of TiN thin films deposited on Si wafers can reach as low as 128 μΩ·cm. TiN thin films showed lower resistivity and worse uniformity with the deposition temperature increasing. In addition, the aging of TiN thin films may weaken the device performance. Optimized deposition parameters were found and full-coverage deposition of thin films on the wall of deep holes with an aspect ratio of approximately 14 has been successfully achieved. The results would be a good reference for the development of 3D capacitors and other microelectronics components.

Fabrication of tantalum silicate films with low TCR and low resistivity by magnetron sputtering

Tantalum silicate (Ta–Si–O) thin film materials have gained significant interest in hybrid renewable energy systems and thin-film resistors due to their exceptional thermal stability and adjustable electrical properties. In this study, we investigated the effects of target compositions and sputtering power densities on the material structures, chemical compositions, microstructures, and electrical properties of Ta–Si–O films. Two target compositions, Ta65(SiO2)35 and Ta80(SiO2)20, were utilized in the deposition process. Notably, we observed substantial variations in the temperature coefficient of resistance (TCR) value and resistivity of Ta–Si–O thin films with different Ta concentrations. Most importantly, when the Ta content of the film is controlled at 62 ± 0.6 % by using this target, the resistivity of the Ta0.62Si0.20O0.18 film can be as small as 2.31 ± 0.05 × 10−4 Ω-cm and has an extremely small TCR of 22 ± 0.4 ppm/°C, which shows an excellent opportunity for the development of precision thin film resistors. A TCR value close to zero can be finely tuned by controlling the Ta concentration in the Ta–Si–O film. These intriguing electrical behaviors were found to be highly correlated with the predominant formation of metallic Ta5Si3 as the main structural phase in the films. This work presents a simple and effective approach to produce Ta–Si–O thin films with near-zero TCR, making them highly suitable for applications under high-temperature conditions. Our findings contribute to the development of tailored thin film materials with desirable electrical properties for advanced electronic and energy devices.

Modeling and Experiments on Temperature and Electrical Conductivity Characteristics in High-Temperature Heating of Carbide-Bonded Graphene Coating on Silicon.

A novel non-isothermal glass hot embossing system utilizes a silicon mold core coated with a three-dimensional carbide-bonded graphene (CBG) coating, which acts as a thin-film resistance heater. The temperature of the system significantly influences the electrical conductivity properties of silicon with a CBG coating. Through simulations and experiments, it has been established that the electrical conductivity of silicon with a CBG coating gradually increases at lower temperatures and rapidly rises as the temperature further increases. The CBG coating predominantly affects electrical conductivity until 400 °C, after which silicon becomes the dominant factor. Furthermore, the dimensions of CBG-coated silicon and the reduction of CBG coating also affect the rate and outcome of conductivity changes. These findings provide valuable insights for detecting CBG-coated silicon during the embossing process, improving efficiency, and predicting the mold core's service life, thus enhancing the accuracy of optical lens production.

Dung Beetle Optimized Fuzzy PID Algorithm Applied in Four-Bar Target Temperature Control System

With the widespread application of infrared thermal imagers in various fields, the demand for thermal imagers and their performance parameter testing equipment has increased significantly. There are particularly high demands on the detection accuracy of minimum resolvable temperature difference (MRTD) testers. Traditional MRTD testers have an issue with the four-bar target temperatures being easily affected by the external environment, resulting in non-uniform temperatures and imprecise detection results. This paper proposes an improvement to the four-bar targets by making them temperature-controllable. Temperature is controlled by installing thermoelectric coolers (TECs) and thin-film platinum resistors at the center and periphery of the four-bar targets with different spatial frequencies. The dung beetle algorithm is used to optimize fuzzy PID parameters to regulate the TEC’s heating and cooling, improving the overall temperature uniformity of the four-bar targets. Temperature simulations of the four-bar targets were conducted on the COMSOL platform, with the control part simulated on the Simulink platform. The simulation results show that, compared to traditional PID, the fuzzy PID controller reduces overshoot by approximately 3.6%, although the system still exhibits mild oscillations. The fuzzy PID controller optimized by the dung beetle optimization (DBO) algorithm, in comparison to standard fuzzy PID, reduces the settling time by about 40 s and lowers overshoot by around 7%, with oscillations in the system nearly disappearing. Comparing the fuzzy PID optimized by the particle swarm optimization (PSO) algorithm with the fuzzy PID optimized by the DBO algorithm, the DBO-based controller shows shorter rise and settling times, further illustrating the superiority of the fuzzy PID control optimized by the dung beetle algorithm. This provides a theoretical foundation for improving the accuracy of MRTD detector measurements. Finally, experimental verification was carried out. The experimental results indicate that DBO (drosophila-based optimization) has significant advantages, and its optimized results are closer to the actual values.

The effect of Al on the corrosion resistance of binary Mg-Al solid solutions: Combining in-situ electrochemistry with combinatorial thin films

The effect of varying Al concentrations on the electrochemical corrosion resistance of binary Mg-Al solid solutions thin films under alkaline immersion conditions was investigated via a combination of in-situ flow-cell, scanning vibrating electrode technique and microscopy analysis. These spatially resolving characterization techniques are employed along the Al concentration gradient of the combinatorically grown thin films enabling efficient screening of the Al concentration dependent electrochemical corrosion behaviour. The analysis revealed an increasing corrosion resistance with increasing Al concentration, as a consequence of Al induced hydroxide reinforcement. Specifically, the addition of >4 wt.% Al decreases the corrosion current density in the range of 70–90 % compared to pure Mg.

Thin Film Resistance Gating by Redox Charge Exchange: Evidence for a Quantum Transition State.

Field effect transistors (FETs) and related devices have enabled tremendous advances in electronics, as well as studies of fundamental phenomena. FETs are classically actuated as fields charge/discharge materials, thereby modifying their resistance. Here, we develop charge exchange transistors (CETs) that comprise thin films whose resistance is modified by quantum charge exchange processes, e.g., redox and bonding. We first use CETs to probe the metallocene-thin film interaction during cyclic voltammetry. Remarkably, CETs reveal transient resistance peaks associated with charge transfer during both oxidation and reduction. Our data combined with kinetics and density functional theory modeling are consistent with a multistep redox pathway, including the formation/destruction of a quantum transition state that overlaps molecule + thin film band states. As a further proof-of-principle demonstration, we also use CETs to monitor n-alkanethiol self-assembly on thin Au films in real-time. CETs exhibit monotonic resistance increase consistent with previously reported fast-then-slow kinetics attributed to thiol-thin film bond formation (charge localization) and etching and/or molecule reorganization.

Effects of annealing on the microstructure and performance of thin-film Pt resistance temperature sensors: experiments and finite element simulations

Platinum resistance temperature sensors have a wide range of applications in various fields, where a high temperature coefficient of resistance (TCR) is a crucial requirement. In this study, thin-film Pt resistance temperature (TPRT) sensors were fabricated on an Al2O3 substrate using a micro-electro-mechanical system (MEMS) based surface micromachining process, and Pt resistance wafers were annealed at a temperature range from 500°C to 800°C using rapid thermal process (RTP). Experimental and simulation results show that TPRT sensors fabricated on the substrate with a rough surface exhibit lower thermal stress. Meanwhile, more pores appear in the Pt thin film, reducing TCR. However, high temperature annealing significantly influences the microstructure of the Pt film and brings about an obvious increase in TCR despite, introducing thermal stress at the interface. Considering the impact of the heat treatment process, the fabricated TPRT sensors demonstrate excellent performance with a TCR of 3512 ppm/°C.

Hydrogen permeation resistance of ZrN thin film deposited by ion-plating

Hydrogen absorption of Zircaloy nuclear fuel cladding, used in light water reactor at nuclear power plants, poses an increased risk of delayed hydride cracking during interim dry storage. Consequently, novel surface technologies aimed at reducing hydrogen absorption have become a critical area of research. Zirconium nitride coatings, renowned for their high hardness, corrosion resistance, and wear resistance, have seen widespread application in various industries, including medical devices, cutting tools, and decoration. This study explores the effectiveness of ZrN coating in suppressing hydride formation in Zircaloy-4, a material commonly used for nuclear fuel cladding. In this research, ZrN coatings were deposited onto recrystallized Zircaloy-4 substrates using a hollow cathode discharge ion-plating (HCD-IP) system. The coated and uncoated Zircaloy-4 samples were then subjected to electrochemical and gaseous hydriding processes. The study further investigates the differences in microstructure and hydrogen content of coated and uncoated Zircaloy-4. From these results, it is evident that the ZrN thin film deposited by HCD-IP exhibited great resistance to hydrogen permeation against both hydriding conditions. It is concluded that the ZrN thin films can serve as an excellent hydrogen barrier layer for Zircaloy-4.

Tailoring the electrical and magneto-electric transport properties of ZnO films via Ti ion implantation

A significant development toward semiconductor-based electronic devices is based on the electric and magneto-electric control of the transport properties of the charge carriers. This study unprecedentedly investigates the Ti implantation and thereafter the effect of structural defects on the electrical and magneto-electric transport properties of Ti-implanted RF-sputtered ZnO thin films. Theoretical stopping and range of ions in matter simulations along with the experimental structural and elemental studies reveal that Ti ion implantation generates a significant amount of oxygen vacancy (VO) defects apart from Ti-related impurities in post-implantation annealed films. The film implanted with 8 × 1015 ions/cm2 (TZO815) exhibits the lowest resistivity (4.68 × 10−3 Ω cm) and the highest carrier concentration (6.61 × 1020 cm−3) values. Resistivity measurements over a temperature range of 5-300K indicate semiconducting behavior for all the films implanted up to fluences of 5 × 1015 ions/cm2 identified with a grain boundary dominated thermally activated band, nearest neighbor hopping, and Mott and Efros–Shklovskii (ES) variable range hopping conduction mechanisms at various temperature intervals. Notably, the gradual decrease in both Mott and ES hopping ranges following Ti implantation indicates the formation of more localized states. Interestingly, the TZO815 film exhibits metal-semiconductor transition around 220 K, suggesting the formation of a degenerate band within the ZnO conduction band upon Ti implantation. Remarkably, the magnetoresistance results align with a semiempirical formula proposed by Khosla and Fischer, indicating that a negative magneto resistance in the TZO thin films is attributed to the spin-dependent scattering of conduction electrons by the localized magnetic moments induced mainly by the implantation induced VO defects.

Regulation of antiphase boundary density in Fe3O4 thin films and its effect on the electrical and magnetic properties

Antiphase boundaries (APBs) widely exist in Fe3O4 thin films and affect significantly their electrical and magnetic properties. Here, effects of APBs on the electrical and magnetic properties of Fe3O4 thin films have been quantitatively investigated by a combined study of pulsed laser deposition, transmission electron microscopy (TEM) and first-principles calculations. It was revealed that the substrates affected greatly the density of APBs in Fe3O4 thin films but did not change the atomic structures of APBs. The APB density in the Fe3O4 (111) thin film grown on the MgO (111) substrate was one order of magnitude larger than that on the Al2O3 (0001) substrate. Atomic-scale TEM characterizations revealed that the APBs in the Fe3O4 thin films on both substrates had three types of atomic structures. Due to the higher APB density in the Fe3O4/MgO thin film, the electrical resistivity at 300 K was two orders of magnitude larger than that of the Fe3O4/Al2O3 thin film. Meanwhile, the saturation magnetization and the coercivity of the Fe3O4/MgO thin film were reduced by 86 % and 35 %, respectively. First-principles calculations suggested that the antiferromagnetic coupling was easily formed at all the three types of APBs, which led to the decrease of spin polarization and the increase of electrical resistance of the Fe3O4 thin films.

Temperature coefficient of resistance and thermal boundary conductance determination of ruthenium thin films by micro four-point probe

Accurate characterization of the temperature coefficient of resistance (α TCR) of electrically conductive materials is pertinent for reducing self-heating in electronic devices. In-situ non-destructive measurements of α TCR using the micro four-point probe (M4PP) technique have previously been demonstrated on platinum (Pt) thin films deposited on fused silica, assuming the thermal conductivity of the substrate as known. In this study, we expand the M4PP method to obtain the α TCR on industrially relevant stacks, comprising ruthenium (Ru) thin films (3.3 nm and 5.2 nm thick) deposited on bulk silicon (Si), separated by a 90 nm SiO2 spacer. The new M4PP methodology allows simultaneous determination of both α TCR and the total thermal boundary conductance (G TBC) between the metallic film and its substrate. We measured the α TCR and the G TBC to be 542 ± 18 ppm K−1 and 15.6 ± 1.3 MW m−2K−1 for 3.3 nm Ru, and 982 ± 46 ppm K−1 and 19.3 ± 2.3 MW m−2K−1 for 5.2 nm Ru. This is in good agreement with independent measurements of α TCR. Our methodology demonstrates the potential of M4PP to characterize thermal properties of metallic thin films used in semiconductor technology.

Hydrogen-included plasma-assisted reactive sputtering for conductivity control of ultra-wide bandgap amorphous gallium oxide

Conductivity control of a-Ga2Ox films by cation/anion off-stoichiometry such as oxygen vacancy formation and hydrogen doping have been achieved by hydrogen-included plasma-assisted reactive sputter deposition system and physical and electrical properties of a-Ga2Ox films formed by this system have been investigated. The change in resistivity of a-Ga2Ox thin films deposited by the hydrogen-included plasma-assisted reactive sputtering was then investigated by changing the H2 flow rate ratio H2/(Ar + H2). The a-Ga2Ox thin films with semiconducting properties with a resistivity as low as 102 Ωcm was demonstrated using the plasma-assisted reactive sputtering system with addition to H2. Along with the low resistivity, the a-GaOx thin films with high film density and band gap energy of 5.2 g cm−3 and 4.8 eV were realized. The electrical resistivity of the a-Ga2Ox thin films can be controlled from 102 Ωcm to 105 Ωcm by appropriately controlling the amount of hydrogen introduced from the plasma. The results indicate that the hydrogen acts as a shallow donor, which increases the carrier concentration, can be efficiently introduced by using the plasma-assisted reactive sputtering system with addition to H2.

Effect of Zinc Oxide Nanostructure on the Electrical Conductivity of Polyvinyl Alcohol (PVA) Thin Films

Zinc oxide nanoparticles in the form of particles and rods were synthesized using the hydrothermal method. The scanning electron microscopy (SEM) examination was performed. The results of the SEM tests showed the nanoscale size of zinc oxide nanoparticles was (75 nm) for particles and (150 nm) for rods. An X-ray diffraction examination was carried out, and a comparison was made between the diffraction pattern of the ZnO nanoparticle and the rods. The results showed that the ZnO nanoparticle is in the hexagonal wurtzite phase of the structure of the particles and rods. Zinc oxide nanoparticles (particles and rods) produced by the hydrothermal method have been used as an additive in polyvinyl alcohol (PVA) polymer matrix to form PVA–ZnO NPs composite thin films. The optical properties of the membrane were studied using ultraviolet–visible examination, which showed a decrease in the energy gap of the composite thin film compared to the pure membrane. While the electrical properties of composite thin film, including resistivity, mobility and majority carrier charge carriers of composite thin film, were measured using the Hall effect measurement. The results showed that zinc oxide nanoparticles have a higher conductivity than nanorods.

Hopping nature of the Hall effect in a samarium nickelate film

We analyzed the temperature dependencies of the DC resistivity and Hall coefficient in thin films of samarium nickelate SmNiO3. A dominating hopping conductivity was revealed in the insulating phase below 400 K, which defines an exponential drop in the Hall coefficient with temperature. The estimated dependencies of the hopping activation energy, Hall mobility, and charge carrier density suggest that small polarons are responsible for hopping. The hopping transport explains the observed sign anomaly of the Hall coefficient in rare-earth nickelates.