Space Charge Limited Conduction Research Articles

Compositional effects of hybrid MoS2–GO active layer on the performance of unipolar, low-power and multistate RRAM device

Currently, 2D nanomaterials-based resistive random access memory (RRAMs) are explored on account of their tunable material properties enabling fabrication of low power and flexible RRAM devices. In this work, hybrid MoS2–GO based active layer RRAM devices are investigated. A facile hydrothermal co-synthesis approach is used to obtain the hybrid materials and a cost-effective spin coating method adopted for the fabrication of Ag/MoS2–GO/ITO RRAM devices. The performance of the fabricated hybrid active layer RRAM device is analysed with respect to change in material properties of the synthesized hybrid material. The progressive addition of 0.5, 1.5, 2.5 and 4.5 weight % of GO to MoS2, results in a hybrid active layer with higher intermolecular interaction, in the case of Ag/MoS2–GO4.5/ITO RRAM device, resulting in a unipolar resistive switching RRAM behavior with low SET voltage of 1.37 V and high I on/I off of 200 with multilevel resistance states. A space charge limited conduction mechanism is obtained during switching, which may be attributed to the trap states present due to functional groups of GO. The increased number of conduction pathways on account of both Ag+ ions and oxygen vacancies (Vo 2+), participating in the formation of conducting filament, results in higher I on/I off. This is the first report of unipolar Ag/MoS2–GO/ITO RRAM devices, which are particularly important in realizing high density crossbar memories for neuromorphic and in-memory computing as well as enabling flexible 2D nanomaterials-based memristor applications.

Development of Lead‐Free Defect Brownmillerite Perovskite Ceramic LiBiFeMnO5 Solid Solution for Electronic Devices

This article reports the fabrication (synthesis) and characterizations (structural, microstructural topographic surface, dielectric, transport, impedance, current–voltage, and resistive properties) of a complex lead‐free defect perovskite material of composition LiBiFeMnO5. A preliminary structural investigation of the X‐ray diffraction pattern using N‐TREOR09 methods shows monoclinic symmetry. The scanning electron microscopic spectrum examines the sample's microstructural topographic surface, fractal study, and roughness (using the standard ISO25178). The analysis of Maxwell–Wagner dielectric dispersion, relaxation, and transport mechanisms is investigated utilizing dielectric, impedance, and conductivity spectrum accumulated within the experimental frequency of (1 kHz–1 MHz) at different temperatures (30–500 °C). A nonoverlapping small polaron tunneling conduction mechanism and correlated barrier hopping mechanism in the material have helped to understand its conduction phenomena. The Ohmic and space–charge limited conduction mechanisms are investigated by the slope of the logarithmic electric field (E) and current density (J). The thermistor constant (β) is determined to be 1982.87. The temperature coefficient of resistance is found to be −0.00419, which may be suitable for negative temperature coefficient thermistors, sensors, and other related devices.

Improvement of switching uniformity in TiO2-based resistive random access memory with graphene oxide embedded film

TiO2-based resistive random access memory (RRAM) devices has the potential to fabricating nonvolatile memory applications. However, the memories based on TiO2 have severe problems like large resistive switching parameter fluctuations, poor cycling endurance and so on, which can be a limitation of the device in practical applications. Graphene oxide (GO) is a novel material that has attracted much attention and is often applied to enhance the performance of memories due to its own special properties. In this work, two types of bilayer structure based on TiO2 for RRAM devices were fabricated. The significant improvement in uniformity of operating voltages and high HRS/LRS ratio of the TiO2-based RRAM were realized by inserting a two-dimensional GO film between TiO2 and FTO. The presence of the GO film would prevent the ion exchange between the electrodes and the switching layer as well as its insulating properties. The conduction mechanisms of all the devices in low and high resistance states were dominant by the Ohmic conduction mechanism and the space charge limited conduction mechanism, respectively. This research manifests the promising potential of two-dimensional GO embedded layer for improving resistive switching performance of RRAMs.

High gain NiO/ZnO heterojunction photodiodes operated in Deep-ultraviolet region

Epitaxially matched (0001) Al2O3 single substrates are utilized to design p-n heterojunctions (p-NiO/n-ZnO) as they offer low defect density for device fabrication due to small lattice mismatches. Using the radio frequency sputtering technique, the NiO/ZnO thin film-based heterojunction has been fabricated by varying the n-type film's (ZnO) thickness for ultra-violet (UV) photodiode application. It has been investigated how different ZnO film thicknesses affect junction parameters and photoresponse properties. The high photosensitivity (∼ 104), enhanced current gain (∼ 105) and fast response obtained at very low UV intensity (0.62μW/cm2) at 300 nm wavelength are attributed to the internal gain mechanism (recombination tunnelling and space-charge limited current conduction with the remarkable effect of the presence of excess free oxygen) in these devices. The prepared heterojunction photodiode with high speed and deep-UV sensitivity can be a potential solution for visible blind UV detection.

Hysteresis loops on voltage-current characteristics and optical responses of PEDOT:PSS/ZnO nanorods/ZnO:Ga heterostructure

Volage (V)-current (I) curves of the poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/ZnO nanorods (NRs)/ZnO:Ga (GZO) heterostructure exhibited a rectification behavior with hysteresis loops both in forward voltage (VF) and reverse voltage (VR) regions. The ultraviolet (UV) light irradiation of 360 nm led to the increase in the reverse current (IR), i.e. generation of photocurrent (PC), and the decrease in the hysteresis loop area in the VF region. In dark, the 1/V vs. ln (I/V2) plot revealed that the dominant carrier transport mechanisms in the low- and the high-VF regions are the direct tunneling and the Fowler-Nordheim (F-N) tunneling through the dipole layer formed at the interface between the PEDOT:PSS and ZnO NRs layers, respectively. On the contrary, the carrier transport in the middle-VF region in dark was dominated by the bulk-limited mechanisms, such as the space-charge-limited (SCL) conduction controlled by the single shallow traps, the trap-free SCL conduction, and the trap-filled-limit conduction controlled by the traps with Gaussian distribution. The UV light irradiation changed the carrier transport mechanism in the middle-VF region to the trap-free SCL conduction. The resistive switching related to the hysteresis loop was found to be caused by the trapping and detrapping of the injected carriers at the traps. In dark, the maximum forward current was increased by the repetition of the VF sweep of 0 V → 5 V → 0 V, but decreased by the repetition of the VR sweep of 0 V → -5V → 0 V, indicating the possibility of the resistive memory. At the low VRs, PC spectra showed a main peak at 350 nm, which is corresponding to slightly higher photon energy than the bandgap energy of ZnO. Moreover, the existence of the tail extending into the bandgap was also observed on the PC spectra. From the time response of PC, the depth of the trap state was estimated to be 0.64–0.77 eV.

Thermal annealing effect on phase evolution, physical properties of DC sputtered copper oxide thin films and transport behavior of ITO/CuO/Al Schottky diodes

Herein, we report on the post-annealing temperature effect on the transport behavior of p-CuO/Al Schottky barrier diodes. In addition, the transformation of phase from Cu4O3 to CuO phase was studied. Copper oxide thin films were grown on soda lime glass substrates, and post-annealing temperature's influence on the films’ structural, chemical, morphological, and electrical characteristics was comprehensively examined. X-ray diffraction study revealed the development of polycrystalline tenorite phase (CuO) on annealing. Raman analysis also confirmed the formation of the tenorite phase (CuO) at higher annealing temperatures (400 °C and 500 °C). XPS study revealed the occurrence of the Cu4O3 phase for room temperature deposited sample and CuO phase at the higher annealing temperature. Using current–voltage analysis, the Chueng model, and the thermoelectric emission model, the Schottky behavior between the metal and semiconductor were investigated. The fabricated diode showed a rectification ratio of 103 at ± 2 V, with the barrier height ranging from 0.84 to 1.12 eV due to different annealing treatments. The attributes of the power law were employed to elucidate space charge-limited conduction and the process of tunneling across the density of interface traps in p-CuO/Al Schottky diodes. This study provides valuable insights into the behavior of the p-CuO/Al Schottky junction, enhancing our understanding of its characteristics.

Defect controlled space charge limited conduction in CdS nanostructured sandwich structure

A defect induced space charge limited conduction mechanism in PVP capped CdS, CdS:Mn and CdS/ZnS nanostructured films has been discussed in this research paper. XRD confirms the hexagonal structure for core CdS and CdS:Mn nanostructure and a mixed type structure for CdS:Mn and CdS/ZnS core–shell nanostructure which agrees with HRTEM measurement. The optical properties shows average band gap around 2.3 eV. The current–voltage (I-V) characteristics of Cu/Film/Cu sandwich exhibit nearly ohmic behaviour at low bias, while at high it become trap induced space-charged limited conduction (SCLC), followed by trap free square law. A quantitative assessment has been done analysing the SCLC mechanism. The shallow traps owing to Mn doping and shelling, found within 0.15 eV to 0.20 eV may exponentially distributed above the electron Fermi level 0.24 eV. The free carrier density, total trap density, trap cross-section, escape frequency are estimated and co-related to growth.

High performance low power multilevel oxide based RRAM devices based on TiOxNy/Ga2O3 hybrid structure

In this study, the resistive memory devices with Ag/TiOxNy/Pt structure and Ag/TiOxNy/Ga2O3/Pt structure are fabricated. The results showed that they exhibit typical resistive behaviors as well as excellent cycling and retention characteristics (>104 s). Especially, the double-layer device with Ga2O3 layer exhibits superior resistive behavior, which has a larger storage window (ON/OFF ratio >105), a smaller set voltage (0.17 V) and a reset voltage (−0.057 V), and lower power consumption (21.7, 0.17 μW) compared with the single-layer device. Furthermore, the Ag/TiOxNy/Ga2O3/Pt device demonstrates ultraviolet light (UV-365 nm)-dependent resistance state (RS), which is advantageous for multilevel memory cells. As the intensity of UV light increases, eight high resistance state (HRS) levels are produced. Finally, the conductive mechanism for both device structures is discussed, and it is found that the conductive filaments mechanism dominates in the low resistance state. However, for the HRS, the single-layer TiOxNy device is dominated by the space charge-limited conduction mechanism, and the double-layer TiOxNy/Ga2O3 device is dominated by the Schottky emission mechanism.

Development of a lead-free colossal dielectric material barium bismuth ferrous oxide for electronic devices

Ceramic materials are promising for the ever-increasing demand in next-generation electronic devices. In this regard, we report the development and characterizations (structural, microstructural surface, dielectric, transport, impedance, resistive and current-voltage properties) of a novel complex material Ba3Bi2Fe2O9. Preliminary investigation of the X-ray diffraction (XRD) pattern shows the dual phase nature (cubic and tetragonal phase). The analysis of the Williamson-Hall plot illustrates the average crystallite size and micro-lattice strain are 91.37 nm and 0.002, respectively. The scanning electron microscopic spectrum examines the microstructural surface interface analysis, fractal study and topographic roughness (using the standard ISO25178). The analysis of Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanisms are investigated utilizing dielectric, impedance, and conductivity spectrum accumulated within the experimental frequency (1 kHz–1 MHz) and temperature (298 K–373 K) range. The energy band of intrinsic and ionization regions with different frequencies (1 kHz and 10 kHz) indicates the semiconducting behavior of the material. The presence of non-Ohmic and space charge limited conduction (SCLC) mechanisms is investigated by the varistor constant β1 and β2. The thermistor constant (β) is determined to be 1683.13, and the temperature coefficient of resistance (TCR) is −0.00903, which may be suitable for wearable NTC thermistors and other related device applications.

Effects of Dy on structural, morphology, optical, and resistive switching properties of HfO2 thin films

This paper studies the effect of Dy on the structure, morphology, and optical properties of HfO2 thin films deposited on fused silica substrates and the optical transparency and resistive switching (RS) behavior of the thin films as an active insulator layer in Ag/active insulator layer/ITO/glass memories. Thin films were deposited by spin-coating using a precursor solution obtained by the Pechini-type sol-gel method. The structural analysis revealed that the insertion of Dy ions into the HfO2 lattice caused the phase transformation from the monoclinic to the cubic phase. Morphological analysis revealed that the thin films had thicknesses between 98 and 101 nm, and their surfaces were composed of 3D islands formed by aggregates of spherical particles ranging from 8 to 5 nm. The active insulator layers had thicknesses ranging from 235 to 218 nm, with no cavities or cracks between them. The optical transparency of the active insulator layer/ITO/glass memory structures was between 70 and 87 %. Optical transmittance, optical bandgap, and optical constants were modified incorporating Dy ions into HfO2 thin films compared to the undoped HfO2 thin films. Incorporating Dy ions into HfO2 increased oxygen vacancies in the active insulator layers. The memory with 10 w% of Dy had the highest resistance off/on ratio of 9.04 compared with undoped HfO2 memory. Also, the conduction mechanism in the high resistive state (HRS) of the memory with 10 w% of Dy was related to ohmic conduction and space charge limited conduction (SCLC).

Effect of Film Density on MgSiO3-Based Resistive Random-Access Memory

Different film density MgSiO3 based resistive random-access memorys (RRAMs) are fabricated to investigate the resistive switching behaviors. The X-ray diffraction results, set voltage, reset voltage, cycling endurance, and retention time are drawn for comparison. With the increasing oxygen ratio gas flow, the resistive switching characteristics of MgSiO3 RRAM are drastically elevated by changing the fabrication conditions of the RS layer. Moreover, we portray a filament model to explain the most likely mechanism associated with the generation and rupture of conductive filaments composed of oxygen vacancies. The high randomness among switching cycles for memory application should be prevented, but it is suitable for the physical unclonable function. The relationship between HRS and the next time set voltage shows a strong correlation, and the conduction mechanisms of the low-resistance state (LRS) and HRS correspond to ohmic conduction and space charge-limited conduction, respectively. Meanwhile, the RRAM undergoes 10,000 s retention tests, and the two resistance states can be distinguished without obvious alternation or degradation. A favorable cycling endurance and retention time achieved by optimizing the fabrication parameters of Cu/MgSiO3/Pt RRAM have the potential for nonvolatile memristors and information security applications.

Smart alloy metalized novel photonic NEMS photodiode with CuAlV/n-Si/Al junction structure

In this work, a novel smart (shape memory) alloy metalized photonic silicon wafer photodiode with Schottky type CuAlV/n-Si/Al contact structure as a nano-electro-mechanical-system (NEMS) photodevice was fabricated by thermal evaporation technique. The CuAlV memory alloy used as the top Schottky metal contact electrode was produced by arc melting technique and a subsequent quenching in an iced-brine water medium, and its shape memory effect characteristics were revealed by thermal and structural tests. The fabricated photonic NEMS photodiode was characterized by different photo-electrical (I-V, I-t) and frequency/time dependent and illuminated capacitance (C–V/f, C-t, C–V/ill.) and conductance-voltage (G-V) measurements under different frequencies and artificial light intensity power conditions. The I-V tests showed an excellent current rectifying ability and very well net photocurrent generation features of the photodiode. The specific detectivity of the photodiode was found as high as almost approaching 1011 Jones. The SCLC (space charge limited current conduction) analyses made on the double-log I-V plots of the photodiode revealed that the trap-filling TFL-SCLC and trap-free SCLC current conduction mechanisms are the two prevailing conduction mechanisms in the forward bias voltage region. The density of interface states (Dit) of the fabricated photodiode was determined. Moreover, an excellent reproducibility of light-induced photocapacitance formation of the novel photodiode was demonstrated by C–V/t measurements under different artificial light power intensities.

Structural and electrical characteristics of Zr-doped HfO2 (HZO) thin films deposited by atomic layer deposition for RRAM applications

In this study, Zr-doped HfO2 (HZO) based resistive random-access memory (RRAM) device were fabricated. The Hf:Zr (1:1) ratio in the HZO films were controlled by changing the HfO2 and ZrO2 cycle ratio during the atomic layer deposition (ALD) process. Next, we studied the structural and electrical properties of the Au/HZO/TiN RRAM device structure. The RRAM devices exhibits an excellent resistance ratio of the high resistance state (HRS) to the low resistance state (LRS) of ~103 A, and as well as good endurance (300 cycles) and retention (>103 s), respectively. Further, the device showed different conduction mechanism in LRS and HRS modes. The lower biased linear region is dominated by ohmic conductivity, whereas the higher biased nonlinear region is dominated by a space charge limited current conduction. This device is suitable for application in future high-density nonvolatile memory RRAM devices.

Investigation of the structural, surface topographical, fractal, capacitive, and electrical properties of a defect brownmillerite perovskite material KBiFeMnO5 for electronic devices.

This article reports the development and characterizations (structural, surface topographical, fractal, dielectric, transport, impedance, resistive, and current-voltage properties) of a defect brownmillerite material KBiFeMnO5. Preliminary investigation of the X-ray diffraction (XRD) pattern with the Monte Carlo technique with McMaille 4.0 shows monoclinic symmetry having lattice parameters: a = 8.261 Å, b = 8.251 Å, c = 7.524 Å, and β = 108.58°. The analysis of the Williamson-Hall plot illustrates the average crystallite size and micro-lattice strain are 124.6 nm and 0.002, respectively. The scanning electron microscopic image examines the microstructural surface topography, fractal analysis, and surface roughness (using the standard of ISO25178) of the material. Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanisms are investigated utilizing dielectric, impedance, and conductivity spectra accumulated within the experimental frequency (1 kHz to 1 MHz) and temperature (25-500 °C) ranges. The energy band of an intrinsic region with a 1 MHz frequency indicates the semiconducting behavior of the material. The logarithmic current density and electric field are used to investigate the presence of ohmic and space charge limited conduction (SCLC) mechanisms. The thermistor constant (β) is determined to be 4633.86, and the temperature coefficient of resistance (TCR) is -0.00322, which may be suitable for high-temperature NTC thermistors and other related device applications.

Synthesis and characterization of (1-x)Bi0.9Sm0.1FeO3 - (x)BaZr0.15Ti0.85O3 based solid solution: Temperature-dependent dielectric and impedance properties

Lead-free solid solution of (1-x) Bi0.9Sm0.1FeO3 − (x) BaZr0.15Ti0.85O3 (BSFO − BZT) (x = 0.0, 0.10, 0.15, 0.20, 0.25, 0.50) ceramics were prepared using solid-state reaction method. The structural, morphological, temperature-dependent dielectric properties and leakage current were investigated. The structural investigation revealed the formation of perovskite structure coexisting with tetragonal and rhombohedral phases within (BSFO–BZT) ceramics. The dielectric measurements (within 303 K-773 K) confirmed the existence of a morphotropic phase boundary at x = 0.15 for the (BSFO–BZT) system. The frequency and temperature dependent electrical behavior were explained using Ac conductivity and impedance analysis. The leakage current behavior for all these samples was investigated using both space charge-limited conduction (SCLC) for bulk and Schottky emission (SE) for limited interface conduction approach, whereas the pure BSFO sample was found to be dominated by ohmic conduction, while the BZT-doped samples were dominated by grain boundary-limited conduction.The sample (0.80)Bi0.9Sm0.1FeO3-(0.15)BaZr0.15Ti0.85O3 achieved largest dielectric constant 330 at 10 KHz along with a moderate leakage current density value of 3.54 × 10-5A/cm2 (which is quite lower than pure BSFO) proven its candidacy to develop a stable photovoltaic, multilayer actuators, and ferroelectric memory devices.

Unveiling the red electroluminescence in LSMO-SRO thin film heterostructures

Herein, intense red electroluminescence (674 nm) in a La0.7Sr0.3MnO3(LSMO)-SrRuO3(SRO) thin films heterostructure obtained by RF-magnetron sputtering is reported for the first time. This novel phenomenon may open a new door in the field of optoelectronics and new generation devices based on multiferroic heterostructure. The structural properties were analyzed using grazing incidence x-ray diffraction demonstrating a rhombohedral structure for LSMO with (024) preferential orientation and an orthorhombic structure for SRO films with (121) preferential orientation. Raman and x-ray photoelectron spectroscopy (XPS) results demonstrated a mix of phases present in LSMO thin films. The thickness analysis was performed using scanning electron microscopy (SEM) in cross section and the thickness was found to be 123 nm and 49 nm for LSMO and SRO, respectively. XPS analysis for LSMO revealed that point defects associate to Mn cations and oxygen vacancies modify the total electrical conductivity and due to Mott transitions, suggest a p-type semiconductor behavior. For the SRO film, the XPS analysis demonstrated a change in the stoichiometry of the film surface, which provides a large amount of oxygen vacancies indicating a metal oxide transition with effects that involve multiple degrees of freedom (charge, spin, and lattice). The electrical behavior observed in the heterostructure corresponds to a metal-semiconductor junction showing a Schottky conduction mechanism in positive bias and a space charge limited conduction mechanism in negative bias. The red electroluminescence effect is discussed considering both a radiative recombination process occurred at the interface due to the presence of Mn2+ ions and an energy transfer mechanism assisted by the migration of the high amount of oxygen vacancies present in the interface.

Self-powered solution-processed photodetectors utilizing FAPbBr3:C60 bulk heterojunction

Hybrid halide perovskites have emerged as pivotal optoelectronic materials due to their easy and cost-effective solution-based manufacturing processes. In this study, we have combined formamidinium lead bromide (FAPbBr3) with buckminsterfullerene (C60) to create the bulk heterojunction (BHJ) photoactive layer for solution-processed photodetectors. Remarkably, the FAPbBr3:C60 BHJ-based photodetectors exhibited a substantial enhancement in optoelectronic performance, with the responsivity increasing from 0.87 A/W to 1.47 A/W compared to the pristine FAPbBr3. This improvement can be attributed to the superior surface morphology and crystallinity of the FAPbBr3:C60 BHJ thin film, which facilitated enhanced charge transport properties. Furthermore, the fabricated photodetectors demonstrated remarkable detectivity even at 0V, enabling self-powered operation. By employing the space charge limited conduction (SCLC) model, we were able to elucidate the dominant charge transport mechanism. At lower voltages, trap-free SCLC was identified as the primary mechanism, while traps governed charge transport at higher voltages. Additionally, we conducted impedance analysis to investigate the underlying factors contributing to the distinctive optoelectronic performance observed in the photodetectors.

High performance resistive random access memory based on Ag/TiO2 Nanorods/FTO for image recognition applications

This study investigates the electrical and synaptic properties of Ag/TiO2 nanorod/FTO-based resistive random access memory (RRAM) devices, focusing on the impact of different seed layer thicknesses on nanorod thickness and RRAM performance. The devices exhibit notable achievements, including a high DC endurance of up to 150,000 cycles, a self-compliance function of 10−2 A, and a resistance switching ratio exceeding 100-fold. Notably, the device with a 3.5 μm TiO2 nanorod thickness demonstrates exceptional stability. Analysis of the IV curve reveals that the switching mechanism is attributed to space-charge-limited conduction (SCLC) resulting from electron trapping in oxygen vacancy traps. Furthermore, the device maintains stable synaptic properties even after undergoing 20 cycles of long-term potentiation and depression. When employed in the context of artificial neural networks for image recognition, these devices attain high accuracy rates in recognizing handwritten digits, achieving approximately 90% accuracy for 8 × 8 pixel images and approximately 88% for 28 × 28 pixel images, demonstrating their suitability for practical applications.

Charge carrier transport mechanism in plasma polymerized methyl acrylate thin films

Plasma-polymerized methyl acrylate thin films (PPMA) of thicknesses 115 to 290 nm were prepared using a capacitively coupled glow discharge plasma reactor. The current density-voltage (J-V) characteristics of the Aluminum/PPMA/Aluminum sandwich configuration were studied between 0.1 and 75 V over the temperature region from 298 K to 398 K for various thicknesses of PPMA thin films. J-V curves show that the conduction current follows Ohm's law in the low voltage area, but that in the high voltage range, the behavior is attributed to be space charge-limited conduction (SCLC) in PPMA thin films. The free carrier density, the trap density and carrier mobility have been determined to be around 1.77 × 1023 to 5.86 × 1023 m−3, 2.84 × 1024 to 3.77 × 1024 m−3, and 3.87 × 10−18 to 69.7 × 10−18 m2V−1s−1, respectively for various thicknesses of PPMA thin films. For the higher temperature and lower temperature areas, the activation energies were found in the range from 0.60 to 0.84 eV and 0.28 to 0.40 eV, respectively for 5 V in Ohmic region and from 0.61 to 0.98 eV and 0.27 to 0.34 eV, respectively for 60 V in SCLC (Non-Ohmic) region, respectively. It is observed that SCLC mechanism in PPMA thin films is dominated by a single dominant trap level/discrete trap level distribution. The PPMA thin films are promising candidates in manufacturing optoelectronic devices.

Direct current conduction mechanism in the methyl acrylate–vinyl acetate composite thin films

Plasma polymerized (PP) methyl acrylate (MA) and vinyl acetate (VA) composite thin films were deposited onto glass substrate varying MA and VA monomer concentrations. Thickness of the composite polymers is observed to vary on the MA and VA monomer ratios, where MA is found more reactive. The FESEM images of the composite polymers show better surface morphology compared to those of the homopolymers. Appearance of broad absorption bands in the FTIR spectra of polymer indicates the structural changes compared to monomer during polymerization. Thermogravimetric analysis and differential scanning calorimetry indicate that composite films are thermally more stable (up to 617 K) compared to homopolymer thin films (563 K). The current density versus voltage (J–V) characteristics of PP(MA-VA) composite films (sandwiched between aluminum electrodes) with different MA and VA ratios showed that the J values of the composite films gradually increase with elevating VA monomer and also with temperature (298–373 K). On the other hand, this value increases with decreasing the thickness of the composite films, which complies with the other studies. The conduction of the thickness-dependent composite films showed Ohmic in nature in the lower voltage region (< 10 V) while the space charge-limited conduction is found to be dominated in the higher voltage region (> 10 V) operating over the entire range of temperature. The activation energy at room temperature was found to be ~ 0.019 eV in the Ohmic region and 0.260 eV in the non-Ohmic region.