Enhancement Of Photosensitivity Research Articles

Enhancement of Photosensitivity in a Low-Operating-Voltage Organic–Inorganic Bilayer Thin-Film Transistor by Using an Asymmetric Source–Drain Electrode

Enhancement of Photosensitivity in a Low-Operating-Voltage Organic–Inorganic Bilayer Thin-Film Transistor by Using an Asymmetric Source–Drain Electrode

Enhancement of photosensitivity and stability of Sn-12 EUV resist by integrating photoactive nitrate anion

The semiconductor industry is currently transitioning to advanced extreme-ultraviolet lithography (EUVL) to address the challenges facing the use of photolithography in microprocessor and memory chip integration. This shift has sparked a surge in novel inorganic EUV photoresist research. However, several technical issues, such as insufficient EUV sensitivity, poor understanding of the photochemistry, and poor stability, have emerged. Here, the EUV sensitivity and stability of state-of-the-art tin oxo clusters are enhanced by integration with the photoactive nitrate anion to give [(BuSn)12O14(OH)6](NO3)2 (TinNO3). The findings of the study reveal that nitrate anions in TinNO3 showing the photosensitivity as low as 32 mJ/cm2 and maintaining stability irrespective of the post-exposure environment. Furthermore, TinNO3 possesses superior resistance to dry etching, enabling selective etching of Si and the amorphous carbon layer. Finally, through intensive optimization of the post-exposure bake parameters, photoresist-substrate adhesion, and development conditions, well-ordered CD 45 nm L/S patterns of TinNO3 thin-film were achieved using ArF lithography.

Magneto-chemical properties of Ti-doped Co3O4 nanosheets for photocatalytic activity applications

The 2D nanosheets of Ti-doped Co3O4 were prepared by hydrothermal technique to understand their dimensional effectiveness for the application of photocatalytic dye degradation. These nanosheets were well characterized for crystal structure, morphology, and composition. The energy band gap for 3% Ti-doped Co3O4 nanosheets was reduced. The 3% Ti-doped Co3O4 shows a reduction in crystallite size, band gap, and an enhancement in saturation magnetization, photosensitivity, and defects. The photocatalytic activity of Ti-doped Co3O4 nanosheets is higher than Co3O4. The small amount of Ti improves the structural, optical, and magnetic properties and photocatalytic action of the as-prepared samples. After successful doping of Ti into Co3O4 lattice the saturated magnetization of Co3O4 was enhanced. The sample 3% Ti-doped Co3O4 nanosheet shows high photosensitivity. The effect of photosensitivity on the photocatalytic activity was scrutinized by I-V characteristics. After being exposed to sunlight 3% Ti-doped Co3O4 nanosheet showed an electrical resistance ∼ 129 kΩ. Also, the effect of oxidizing reagents (H2O2) and reducing reagents (scavengers) was studied in detail. The photocatalytic efficiency enhances up to 97.29% under sunlight irradiation within 20 min only. The effect of magnetism on enhancement of efficiency for MB dye degradation was discussed in detail. The charge transfer, reducing charge carrier recombination, and increasing the utilization of light energy in catalytic processes were presented in this report at length.

Photoconductivity of functionalized carbon nanotubes

Investigation of carbon nanotubes is a modern trend due to their combination of unique physical, chemical, electrical, and optical properties. Carboxyl-functionalized carbon nanotubes (fCNTs) for investigation of photoelectrical properties were synthesized. The photo-sensitivity spectra of a carboxyl-functionalized CNT sample for voltage range from 1 to 9 V, and for the spectral range from 400 to 900 nm were investigated. The voltage equal to 1 V generated lower photosensitivity in the broadband wavelength range for visible to near-infrared. The most efficient photocurrents of fCNTs were received for a voltage of 5 V in the wavelength range λp~400-800 nm and for voltage U=3V in the broadband spectral range λp~400-900 nm. The experimental data analysis helped to determine the widest photosensitivity range, as well as the highest sensitivity value. As result, the voltage U=5V was obtained. Here, the most significant photocurrent peak with Ip~2.67 μA for wavelength λ~720 nm was observed. A comparison between the photosensitivity spectra of fCNTs and pure CNTs shows that the photosensitivity of fCNTs has increased significantly. Thus, the maximum photosensitivity for fCNTs is Ip ~ 2.67 μA, and for pure CNTs, it equals Ip ~ 0.185 μA. A 14-fold enhancement of photosensitivity for fCNT has been registered. The mathematical analysis of spectral dependencies of generated photocurrents under different applied voltages can be described using fourth-order polynomials. The I-V characteristics for wavelengths 760 nm and 780 nm have the same trend with the shift of photocurrent maximum to the lower parameters of voltage. The carboxyl-functionalized nanotubes can be effectively used as light detectors and in optoelectronic applications.

Organic Phototransistor with Light-Induced Contact Modulation and Sensitivity Enhancement Using a C60/C70:TAPC Hybrid Channel.

Organic phototransistors (OPTs) are attracting a significant degree of interest as devices that have the potential to play multiple roles, including light sensing, signal amplification, and switching for addressing when they are used for matrix arrays. However, it has been challenging to realize OPTs that can perform all of these roles simultaneously at a sufficient performance level because the channel materials with high carrier mobility often exhibit relatively low photoabsorption. In this work, we propose OPTs with a hybrid bilayer channel consisting of a neat C60 layer and a bulk-heterojunction layer of C70 and 1,1-bis(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (TAPC) as a possible solution to this issue. While the C60 layer serves as the main carrier-transporting layer with high mobility, the C70:TAPC layer operates as a photoactive layer wherein the photogenerated carriers provide photoinduced contact modulation that leads to a significant enhancement in photosensitivity. With the optimal design maximizing the absorption, the proposed hybrid-channel OPTs show a responsivity of ca. 180 A/W, which is 4.5 times higher than that of the control OPT with a C70:TAPC single channel. The operation mechanism and the origin for the improvement are verified by an in-depth analysis of the photoinduced modulation of the channel and contact resistances of the OPTs.

Plasmon enhancement of photosensitivity of Ag–chalcogenide glass thin film structures

In this paper, we present the results of studying the features of plasmon- enhanced photostimulated diffusion of silver into thin films of chalcogenide glasses (ChG), in particular, As 2 S 3 and GeSe 2 . To ensure excitation of surface plasmon-polaritons (SPPs) at the interface between silver and ChG films, silver diffraction gratings with periods of 899 and 694 nm were used as substrates. The samples were exposed to the p-polarized radiation of a He-Ne laser (λ = 632.8 nm). The radiation of the same laser, attenuated by two orders of magnitude, was used to detect SPP, which enabled to study the kinetics of photostimulated processes in the thin-layer structure of Ag–ChG. It has been established that in the initial period of exposure, the SPP electromagnetic field significantly enhances the photostimulated flux of silver ions in ChG (by 2-3 times). The photodissolution kinetics of Ag in ChG is defined by the features of the granular structure of the investigated thin chalcogenide films. For the GeSe 2 film with the effective thickness 8 nm, the kinetics of the film refractive index increase caused by silver photodoping is well approximated by a logarithmic dependence. For the Ag–As 2 S 3 structure (the effective thickness of the As 2 S 3 film is 14.8 nm), this kinetics is closer to the linear one; moreover, for photodoping without SPP excitation, the kinetics is somewhat superlinear, while with plasmon excitation, it is sublinear. The main physical mechanism responsible for the acceleration of the process of photostimulated diffusion in the structure under study appears to be an accelerated generation of electron-hole pairs, which takes place in the ChG layer near the interface with the metal, where the SPP electromagnetic field strength is maximum, and/or plasmon- assisted hot carrier generation due to plasmon scattering on the surface of the metal film and subsequent internal photoemission of electrons from silver into chalcogenide.

Significant enhancement in photosensitivity, responsivity, detectivity and quantum efficiency of Co3O4 nanostructured thin film-based photodetectors through Mo doping developed by spray pyrolysis method

Herein, we have developed the high-performance photodetector diodes (p-Co3O4/n-Si and p-Mo@Co3O4/n-Si) by spray pyrolysis route for modern optoelectronic devices. The impact of different molybdenum (Mo) ions concentrations (0, 2, 4, and 6 wt.%) on the structural, morphological, optical and photo-electrical properties of Co3O4 films has been investigated. The X-ray diffraction study confirms the cubic phase of Mo-doped Co3O4 thin films with good crystallinity. From FESEM images, the unevenly sized sphere-like grains were clearly observed which are agglomerated at higher doping levels. UV-VIS spectra confirmed that the thin film owns good absorption and the energy gap varied with Mo doping. The p-Co3O4/n-Si and p-Mo@Co3O4/n-Si (Mo = 2, 4, and 6 wt.%) photodiodes were fabricated. The barrier height of the fabricated diodes was varied in the range of 0.65 to 0.98 eV. The maximum sensitivity of 10382% at 1.2 V has been achieved for 6 wt.% of Mo-doped diodes due to the creation of photo-created charge couples. Also, the quantum efficiency of the diode was enhanced from 39 to 164%. The 6 wt.% of p-Mo@Co3O4/n-Si junction diode exhibited the highest device performance among others and can be used as high performance photodetector.

Characterization of ZnSxSe1-x films grown by thermal co-evaporation technique for photodetector applications

Zinc sulfoselenide (ZnSxSe1-x, 0.0 ≤ x ≤ 1.0) films were prepared by thermal co-evaporation by taking ZnS and ZnSe as the source materials. The structural and optical properties confirm the composition variation where a systematic shift in the X-ray diffraction peak and absorption edge of the films was witnessed with variation in ‘x’. As ‘x’ varied from 0.0 to 1.0, the bandgap of the films has changed from 2.56 eV to 3.50 eV. The presence of sulfur and selenium vacancy in the deposited films has been confirmed by analysis of photoluminescence spectra. Raman and X-ray photoelectron spectroscopy studies explained the chemical state and revealed the incorporation of oxygen that helped in the enhancement of electrical conductivity and photosensitivity of the samples. The electrical parameter carrier density and resistivity were dependent on the composition parameter and crystallite size of the films. All the films showed n-type conductivity and samples with x = 0.4 showed high photo-response (photosensitivity > 20 for white light) and were suitable for photodetector application. These films showed maximum response (photosensitivity > 20) at 500 nm.

Elucidating the influence of native defects on electrical and optical properties in semiconducting oxides: An experimental and theoretical investigation

Defect engineering using self-doping or creating vacancies in polycrystalline oxide based materials has profound influence on optical absorption, UV photo detection, and electrical switching. However, defects induced semiconducting oxide devices show enhancement in photo detection and photosensitivity, and hence still remain interesting in the field of optoelectronics. In this study, defect engineering in semiconducting oxide materials is discussed along with their roles in optoelectronic device-based applications. Theoretical investigations have been done for identifying defect states by performing first-principles electronic structure calculations, employing the density-functional theory. Particularly, in this work we have focused on probing the defect-induced changes in optical and electrical processes by means of experimental as well as computational investigations. Hence, systematic experimental measurements of optical absorption, electrical switching, charge density, and photocurrent in defect-rich semiconducting oxide samples have been performed. Our results suggest that defects can lead to enhancement of optoelectronic properties such as photocurrent, switching speed, optical absorption etc. for semiconducting oxide based devices.

Enhanced photosensing by Mg-doped ZnO hexagonal rods via a feasible chemical route

One-Dimensional (1D) pure-ZnO, Zn0.9Mg0.1O and Zn0.8Mg0.2O thin films have been successfully grown over a glass substrate using simple economical chemical bath deposition method (CBD). This investigation explores the enhancement in photocurrent and photosensitivity of Zn1−xMgxO thin films via induced defects with vertically aligned hexagonal rod-like array thin films. The structural, optical and electrical properties of the synthesized materials have been elucidated using X-ray Diffraction (XRD), Raman, UV–Vis spectroscopy, Photoluminescence (PL), and I–V characteristics. Hexagonal rod-like morphology has been confirmed from both XRD and SEM results. Change in structural properties revealed that the formation of the Mg(OH)2 phase for Zn1−xMgxO thin films from XRD spectra. Thus, the impact of extra Magnesium (Mg) which is difficult to incorporate in ZnO lattice sites which causes the phase segregation and possibly creates morphological and structural defects. This has been also confirmed from electron–phonon interaction in Raman analysis. Such as the Raman-shift of E2 (high) mode in Zn1−xMgxO thin films towards higher frequencies indicates the substitution of Mg at O lattice sites. However the formation of phase segregation had a significant effect on optical as well as electrical properties of the ZnO hexagonal rods thin films. From UV–Vis spectra, the intensity of absorption edges for Mg-doped samples are decreases while the optical band gaps are increases from 2.87 to 3.47 eV and also from PL spectrum shows that the defect states in visible range are increases with increasing Mg content in ZnO. The parameters like photocurrent and electrical resistance are calculated from I–V characteristics and the results shows that the photosensitivity enhanced as Mg content increases in ZnO.

Cubic tin sulfide thin films by a Sn-NTA system based chemical bath process

SnS films were prepared by a chemical bath deposition process in which the concentration of nitrilotriacetic acid, acting as the complexing agent, promoted an increase in film thickness, better grain connectivity, and the formation of single-phase cubic π-SnS. The optical and electrical studies in these films demonstrated that the enhancement of photosensitivity from 19.59 to 22.5 was associated with the elimination of the SnS2 phase, which consequently led to a band gap narrowing from 1.82 to 1.77 eV.

Enhancement of photosensitivity of thermally evaporated crystalline PbS thin films by low energy oxygen ions implantation

This study presents the effect of low energy (120 KeV) O-ions implantation on the photosensitivity of PbS thin films by vacuum thermal evaporator (VTE). The crystallite size (D) of PbS films decreased from 32.8 nm to 17.4 nm and the bandgap (E g) increased from 1.61 eV to 1.76 eV as the fluence increased from 0.5 × 1016 ions cm−2 to 1.5 × 1016 ions cm−2. The PL spectra of O-ions implanted PbS thin films showed a dominant peak at 381 nm regardless the fluence of implantation. The photocurrent sharply increased by the implantation of O-ions (0.5 × 1016 ions cm−2) due to the creation of ‘shallow traps’ in the forbidden gap of PbS thin films under illumination of visible light (100 mW cm−2). The highest photosensitivity of O-ions implanted PbS thin films was observed due to the creation of proper traps for the photoconduction for the particular dose of 0.5 × 1016 ions cm−2.

Surface-Plasmon-Induced Ag Nanoparticles Decorated In2O3 Nanowires for Low Noise Photodetectors

Silver (Ag) nanoparticles (NPs) were synthesized by glancing angle deposition (GLAD) technique on indium oxide (In2O3) nanowires (NWs) over n-type Si substrate. The In2O3 NWs and Ag NPs were morphologically characterized by field emission scanning electron microscopy (FESEM) and electron dispersive spectroscopy (EDS). The complete growth of In2O3 NWs was observed by high-resolution transmission electron microscopy (HRTEM) and corresponding selected area electron diffraction (SAED) pattern was also studied. The structural analysis was done by high-resolution X-ray diffraction (HRXRD), and relevant peaks were identified to calculate the crystalline size. The HRXRD patterns displayed the peak for Ag NPs and monoclinic crystal structure of Ag3O4. The optical properties were analyzed by photoluminescence (PL) emission spectrums. The presence of Ag NPs over In2O3 NWs reduced the PL intensity. Atomic force microscopy (AFM) was also studied to estimate the surface roughness for both the samples. The semi-logarithmic I-V (ln(I)-V) characteristics revealed the enhancement in photoconduction for the n-Si/In2O3 NWs/Ag NPs device at − 4.5 V using a 100-W tungsten filament source. The total ~ 2.6 fold enhancement in photosensitivity were recorded for the n-Si/In2O3 NWs/Ag NPs device at an applied voltage of − 2.4 V. This n-Si/In2O3 NWs/Ag NPs device possessed high detectivity and low noise equivalent power (NEP) as compared with the bare n-Si/In2O3 NWs device.

Effect of gamma irradiation on structure and photoconductivity of amorphous Sb30Se70 chalcogenide films

The development of new materials and their processing have recently got increased attention for improving the device efficiencies for next generation solar cells. This investigation reports the effect of gamma radiation on structure-property relationship for thermally evaporated amorphous Sb30Se70 films. Amorphous/crystalline nature and molecular structure was examined by X-ray diffraction and Raman spectroscopic techniques respectively. The growth of Se crystallites in amorphous network accompanied with variation of characteristic Raman bands for Sb-Se (187 cm−1) and Se–Se (252 cm−1) vibrations have been observed. Optical gap and tailing parameter exhibit an inverse relation with γ-doses. Photoconductivity measurements revels the enhancement in photosensitivity (~27%) at 50 kGy dose and then decreases with further increase in radiation dose. The photocurrent decay data has been fitted to stretched exponential function and related parameters are reported. These results are very vital for developing new materials or processes for improving the efficiency of photovoltaic devices.

Improved optical and structural properties of cadmium sulfide nanostructures for optoelectronic applications

In this study, the effect of ZnO seed layer on the growth of uniform CdS nanostructures was investigated using chemical bath deposition technique. Besides, the influence of molar concentration of reagents on the surface morphology, structural and optoelectrical properties of the deposited CdS thin films were examined. The CdS nanostructures were grown on bare glass and ZnO/glass substrates with different reagent molar concentrations. The results indicated an improvement in the homogeneity and uniformity of the grown CdS nanostructures on ZnO seed layer which can be due to the low lattice mismatch between ZnO and CdS structures. The CdS/ZnO samples were optimized by changing the molar concentration of reagents. A three–dimensional intersecting vertical nanosheet morphology with hexagonal structure was obtained when modified chemical concentration of 0.5 M was applied. The XRD pattern of CdS nanosheets indicated the hexagonal phase of CdS which were strongly orientated along (002) plane. The elevated intensity of dominant peak related to this sample confirmed the improved crystal quality of this CdS nanostructure comparing to the other samples. The UV–Vis spectrum demonstrated a high absorption coefficient for CdS intersecting nanosheets which might be due to the high specific surface area and light trapping behavior of this sample. The photoluminescence study also showed an improvement in optical properties of optimized CdS nanostructures. In order to study the optoelectrical properties of CdS nanostructures, metal–semiconductor–metal photodetectors were fabricated with different CdS samples and their current–voltage characteristics were analyzed. The results indicated an enhancement in photosensitivity, responsivity, and speed of photodetectors based on optimized CdS nanostructures.

Graphene-Assisted All-Fiber Optical-Controllable Laser

All-optical controlling provides the burgeoning, precise, and compact access in photonics and optoelectronics with tunable performance. Through tuning physical parameters of optical-controlled devices, such as effective index, bandwidth and dispersion, the output characteristics of free-running lasers can be manipulated for widespread applications in spectroscopy and laser biology. Among which the flexible optical-thermal tunability of graphene introduces an advantageous avenue for the enhancement of photosensitivity of optical-controlled devices to efficiently regulate laser properties. Here, we fabricate an optical-controllable fiber filter based on a graphene-assisted micro-fiber Bragg grating, whose wavelength can be linearly tuned by controlling pump light, and a tuning step of 3.1 pm is achieved. By cooperating it with a fiber laser operating at a Q-switched mode-locked state, the lasing wavelength is all-optically controlled with a linear tuning sensitivity of 23.5 pm/mW. Considering the optical controlling performances, such a wavelength-tunable fiber laser may find potential applications in all-optical computing, all-optical logic gating, and generation of microwave source.

The flexible-transparent photosensitive films of cotton cellulose framework of carbon quantum dots/ZnO

The flexible-transparent photosensitive films of cotton cellulose framework of carbon quantum dots (C QDs)/ZnO were prepared by electrospinning-hydrothermal method. The results demonstrated that these films exhibited obvious enhancement of photosensitivity and flexible stability. Further, this enhanced photoconductivity and flexible stability could be attributed to C QDs with unique up-converted photoluminescence and cotton cellulose with flexibility and physical-chemical stability.

Synergetic Enhancement in Photosensitivity and Flexibility of Photodetectors Based on Hybrid Nanobelt Network

AbstractHigh photosensitivity, transparency, flexibility, and facile assembly are the main important features of photodetectors, which extend their use for vast range of applications. In this study, a highly stable transparent flexible ultraviolet–visible (UV–vis) hybrid photodetectors, with enhanced photosensitivity and fast photoresponse speed (on/off switching) based on In2O3‐ZnO hybrid nanobelts, is reported. A highly enhanced photosensitivity of about 4.7 × 105, fast photoresponse, and at the same time extended spectral range (UV to vis) have been achieved in these hybrid flexible photodetectors as compared to their pure counterparts In2O3 and ZnO. Furthermore, these photodetectors have shown excellent photoresponsivity of 18.5 A W−1 with an external quantum efficiency 7.4 × 103% and a high detectivity of 1.7 × 1012 Jones under the excitation wavelength of 308 nm. A facile, tunable, and cost‐effective method has been employed to assemble these photodetectors by using well‐aligned electrospun nanobelts. The prepared UV–vis photodetectors have shown a high transparency >90% under visible light (400–700 nm) which demonstrates their applications in fully light exposure required devices. These transparent electrospun nanobelts with high aspect ratios can also be transferred to multiple substrates, which shows their applications in different environment as a freestanding nanobelt network for UV–vis photodetectors.

Synthesis of copper doped Zinc oxide nanowires with enhanced ultraviolet photoresponse behavior

This work mainly focused on the synthesis of copper doped zinc oxide nanowires by hydrothermal method, their characterization and their ultraviolet (UV) light sensing response at room temperature. The structural and morphological characterization was carried out using X-ray diffraction and scanning electron microscopy. Enhanced ultraviolet (UV) photodetection property has been achieved for a dopant concentration of 2.5wt% and 5wt% showing UV photosensitivity values (photo-to-dark current ratio) of around 800 and 1800, respectively. This is an order of magnitude higher than the undoped ZnO nanowires. High photocurrent gain is attributed to the trapping of carriers under dark and detrapping them under UV illumination by Cu-related defects. Enhancement in photosensitivity indicates that Cu-doped ZnO nanowires are promising candidates for UV photodetection applications.

Enhanced UV–vis photoconductivity and photoluminescence by doping of samarium in ZnO nanostructures synthesized by solid state reaction method

In the present work, polycrystalline undoped and samarium doped zinc oxide (ZnO) nanostructures were successfully synthesized by solid state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis absorption spectroscopy, photoluminescence study and photoconductivity study. XRD patterns revels that the samples possess hexagonal wurtzite structure of ZnO without any secondary phase after samarium doping. The crystallite size is calculated by Debye–Scherer's formula. Williamson–Hall analysis reveals presence of strain in synthesized samples. SEM micrographs show spherical and oblate type shape of nanoparticles. UV–vis absorption study shows blue shift in absorption band edge in undoped as well as in samarium doped ZnO nanoparticles as compared to its bulk counterpart. Photoluminescence spectra of the samples show peaks corresponding to near band edge UV emission and defect related emissions in the visible region. In photoconductivity study, enhancement of photosensitivity has been observed in 1% Sm-doped ZnO sample while the maximum photocurrent is found in 3% Sm-doped sample. The variation of dark current and photocurrent with applied voltage exhibits super-linear nature. The rise and decay of photocurrent indicate anomalous behavior during steady state illumination.