عباس محمد سلمان العباسي

Gallium nitride (GaN) nanocrystalline (NC) thin films (TH) were deposited on different surfaces of material as substrates; quartz, glass as well as fluorine-doped tin oxide (FTO) using radio frequency (RF) reactive magnetron sputtering method. The effects of substrate type on structural and morphological properties of GaN-NCTH were studied. X-ray diffraction analyses and field-emission scanning electron microscopy (FESEM) images showed that the GaN particles have covered all surfaces of the substrates with a smooth arrangement. The root mean square (RMS) surface roughness was 30.8, 1.45 and 1.46 nm for the GaN-NCTH deposited on FTO, glass and quartz substrates, respectively. Based on the GaN-NCTH prepared onto glass substrate, the optical bandgap was calculated to be 3.38 eV.

Core-shell self-powered SiNWs homojunction photosensors have been fabricated. SiNWs are prepared by a metal assisted chemical etching method using different HF/H2O2 ratios and etching times. The length of the p-SiNWs increased as the H2O2 concentration and etching time increased. All the grown SiNWs show very low (∼0.7%) optical reflectance for the wavelength range of 200–1100 nm. Photoluminescence spectra of all prepared SiNWs show sharp and broad emission bands located in the red region of the light spectrum. Core-shell homojunction photosensors were fabricated by spin coating P2O2 onto the surface of the prepared p-SiNWs and annealed at 900 °C for 1 h. The fabricated devices exhibited photovoltaic behavior and high photosensitivity with fast response speed to the visible light. However, the sample that was fabricated using HF/H2O2 ratio of 1:1 showed the highest photosensitivity value of 3578% while the photosensor prepared using 2:1 ratio of HF/H2O2 gave the faster rise and decay time.

Cuprous oxide (Cu2O) nanocrystalline thin films were prepared on two types of substrates known as crystalline silicon and amorphous glass, by radio frequency reactive magnetron sputtering method. Scanning electron microscopy images confirmed that Cu2O particles covered the entire surface of both substrates with smoothing distribution. The root mean square surface roughness for the prepared Cu2O thin films on glass and Si (111) substrates is 4.16, and 3.36 nm, respectively. Meanwhile, X-ray diffraction results demonstrated that the two phases of Cu2O and CuO were produced on Si (111) and glass substrates. The optical bandgap of Cu2O thin films synthesised on glass substrate is 2.42 eV. Furthermore, the prepared Cu2O nanocrystalline thin films have showed low reflectance value in the visible spectrum. Metal-Semiconductor-Metal photodetector based Cu2O nanocrystalline thin films deposited onto Si (111) was fabricated using aluminium and platinum, with the current-voltage and photoresponse characteristic investigated under various applied bias voltages. The fabricated Metal-Semiconductor-Metal (M-S-M) photodetector had shown 126% sensitivity in the presence of 10 mW/cm2 of 490 nm light with 1.0 V bias, displaying 90 and 100 ms response and recovery times, respectively. These findings have demonstrated the suitability of M-S-M Cu2O photodetector as an affordable photosensor in the future.

In this study, the effect of duration on the growth of rutile TiO2 nanostructures (Ns) deposited onto the p-Si (111) substrate on the structural, morphological, and optical properties of rutile TiO2 Ns has been investigated. All Si substrates were seeded with a TiO2 seed layer synthesized using a radio-frequency (RF) reactive magnetron sputtering system. Chemical bath deposition method (CBD) was employed to grow rutile TiO2 Ns on seeded Si substrates at duration time of growth (1, 2, 3, and 4 h). X-ray diffraction, Raman spectroscopy,and field-emission scanning electron microscopy (FESEM) analyses demonstrated the tetragonal rutile structure of the synthesized TiO2 Ns with the highest (110) peak intensity. Optical properties were investigatedby using photoluminescence (PL) spectroscopy of the grown rutile Ns, with the spectra exhibiting the sharpest (smallest FWHMs) and highest peak revealed the high quality of TiO2 Ns with few defects was found for the sample prepared for 3 h, which reflects the crystalline quality. These results show that the optimized growth conditions yield very high quality TiO2 Ns on p-type (111)-oriented silicon substrates. A fast-response p-n heterojunction photodiode was fabricated by depositing Al contacts on the front of the optimal sample via RF reactive magnetron sputtering. Upon illumination of a pulsed UV light (325 nm, 1.6 mW/cm2) at 5 V bias voltage, the device showed 3.8 × 102 sensitivity, the photoresponse peak was 460 mA/W, the response and recovery times were 50.8 and 57.8 ms, respectively.

The fabrication and characterization of a metal–semiconductor–metal ultraviolet photodetector are studied. The photodetector is based on TiO2 nanorods (NRs) grown on p-type (1 1 1)-oriented silicon substrate seeded with a TiO2 layer is synthesized by radio frequency reactive magnetron sputtering. A chemical bath deposition is used to grow TiO2 NRs on Si substrate. The structural and optical properties of the obtained sample are analyzed by using X-ray diffraction and field emission-scanning electron microscopy. Results show a tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties are further examined using photoluminescence spectroscopy. A sharp and high-intensity UV peak at 367 nm is observed in comparison with visible defect peaks centered at 432 and 718 nm. Upon exposure to 365 nm light (2.3 mW/cm) at 5 V bias, the device displays 76.06 × 102 sensitivity, internal photodetector gain of 77.06, photocurrent of the device is 2.62 × 10−5 A and photoresponse peak of 69.7 mA/W. The response and recovery times are calculated as 18.5 and 19.1 ms upon illumination to a pulse UV light (365 nm, 2.3 mW/cm2) at 5 V applied bias. These results demonstrate that the fabricated high-quality photodiode is a promising candidate as a low-cost UV photodetector for commercially-integrated photoelectronic applications.

The effects of annealing treatment on growth of TiO2 nanostructures (Ns) on the structural and morphological properties were studied. The phase transformation also investigated in this study. TiO2 Ns were fabricated on p-type (111)-oriented silicon substrates. Chemical bath deposition (CBD) method was employed to grow TiO2 Ns on the Si substrate at different annealing temperatures (without annealing, 350, 550, 750, and 950 °C). The sample prepared at an annealing temperature of 550 °C had a high crystallinity. A metal–semiconductor–metal type humidity sensor device was fabricated by depositing Pt contacts on top of the optimal sample (the sample annealed at 550 °C) and the device working at room temperature, environmentally friendly features, and uncomplicated low-cost fabrication.

In this work, gallium nitride (GaN) layers were successfully grown on Flat-Si and porous silicon (PSi) using a radio frequency-magnetron sputtering system. Field emission scanning electron microscopy and atomic force microscopy images showed that the grown film on Flat-Si had smoother surface, even though there were some cracks on it. Furthermore, the X-ray diffraction measurements showed that the peak intensity of all the grown layers on PSi was higher than that of the grown layer on Flat-Si. Our detailed observation showed that PSi is a promising substrate to obtain GaN films.

Mg doped ZnO (Mg:ZnO) nanrood (NR)-arrays have been successfully fabricated onto p-type Si substrate via hydrothermal method. The photoluminescence spectra of Mg:ZnO reveal the existence of residual surface defects as deep level in the visible range. Reliable approach was used to completely remove the surface defects in order to obtain high optical quality of Mg:ZnO NR-arrays in the UV region. RF sputtering was used to deposit MgO nanoparticles around the Mg:ZnO NRs to suppress the entire surface defects. Morphological observations reveal the formation of well-aligned nanorods grown perpendicularly to substrate surface. The hexagonal structure of Mg:ZnO NR-arrays oriented along c-axis favors the formation of core-shell Mg:ZnO/MgO NR-arrays. Photoluminescence spectra of the as-fabricated core-shell Mg:ZnO/MgO exhibit an intense peak near-band-edge (NBE) emission at 375 nm which completely result in the disappearance of the deep level emission at around 580 nm, achieving a maximum intensity ratio (∼140) of IUV/IVIS. The Raman E2 (high) mode of Mg:ZnO NR-arrays showed a blue shift compared to ZnO NR-arrays associated with the strain arising from Mg:ZnO core.

This study aimed to investigate the effects of variations in precursor concentration (TiCl3 solution) on the structural, morphological, and optical properties of rutile titanium dioxide (TiO2) nanorods and fabricated metal–semiconductor–metal UV detector depending on the optimal sample. The nanorods were prepared from an aqueous solution of titanium (III) chloride (TiCl3) on p-type, (1 1 1)-oriented Si substrates at different concentrations of TiCl3 solutions (2, 3, 4, and 5 mM). The experimental results showed that the TiO2 nanorods grown at 4 mM concentration exhibited optimal structural properties. A fast-response metal–semiconductor–metal UV detector was fabricated by depositing Pt contacts on the front of the optimal sample via RF reactive magnetron sputtering. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias voltage, the device showed 44.4 sensitivity. In addition, the internal gain was 1.45, and the photoresponse peak was 70 mA/W. The response and the recovery times were calculated to be 7.8 ms upon illumination to a pulse UV light (365 nm) at 5 V bias voltage.

Rutile-phase titanium dioxide nanorods (NRs) were synthesized successfully on p-type silicon (Si) (1 1 1), c-plane sapphire (Al2O3), glass coated with fluorine-doped tin oxide (FTO), glass, and quartz substrates via chemical bath deposition method. All substrates were seeded with a TiO2 seed layer synthesized with a radio frequency reactive magnetron sputtering system prior to NRs growth. The effect of substrate type on structural, morphological, and optical properties of rutile TiO2 NRs was studied. X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy analyses showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were examined with photoluminescence (PL) spectroscopy of the grown rutile NRs on all substrates, with the spectra exhibiting one strong ultraviolet emission peak intensity compared with broad visible peak. The optimal sample of rutile NRs was grown on Si substrate. Thus, a fast-response metal–semiconductor–metal ultraviolet (UV) detector was fabricated. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias, the device displays 2.62 × 10−5 A photocurrent, and the response and recovery times are calculated as 18.5 and 19.1 ms, respectively. These results demonstrate that the fabricated high-quality photodiode is a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

An ultraviolet photodiode based on rutile TiO2 nanorods, which were grown on p-type Si substrate seeded with a TiO2 layer, was synthesized by radiofrequency reactive magnetron sputtering. Chemical bath deposition was performed to grow rutile TiO2 nanorods. X-ray diffraction and field emission-scanning electron microscopy were conducted to determine the structural and optical properties of the sample. The synthesized TiO2 nanorods exhibited tetragonal rutile structure. The device showed 3.79 × 102 sensitivity when it was exposed to 325 nm light (1.6 mW/cm) at 5 V bias voltage. In addition, the internal gain of the photosensor was 4.792 and the photoresponse peak was 460 mA/W. The photocurrent was 6.09 × 10−4 A. The response and recovery times of the PD were 50.8 and 57.8 ms, respectively, upon illumination of a pulsed UV light (325 nm, 1.6 mW/cm2) at 5 V bias voltage

A structure for ultraviolet (UV) photosensor based on rutile TiO2 nanorods (NRs) grown on p-type (111) - oriented silicon substrate seeded with a TiO2 layer synthesized by radio-frequency (RF) reactive magnetron sputtering has been fabricated. Chemical bath deposition (CBD) was carried out to grow rutile TiO2 NRs on Si substrate. The structural and optical properties of the sample were reported by X-ray diffraction (XRD) and field emission-scanning electron microscopy (FESEM) analyses. Results showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were further examined by photoluminescence spectroscopy, and a high-intensity UV peak centered at around 366 nm compared with visible defect peaks centered at 436 and 716 nm was observed. Upon exposure to 365 nm light (2.3 mW cm -2) at 5V bias voltage, the device showed 62.8 × 102 sensitivity. In addition, the internal gain of the photosensor was 63.8, and the photoresponse peak was 467 mAW-1. Furthermore, the photocurrent was 6.7 × 10-4 A. The response and the recovery times were calculated to be 48 and 40 ms, respectively, upon illumination to a pulsed UV light (365 nm) at 5V bias voltage. All of these results demonstrate that this high-quality photosensor can be a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

In this work, nanoflower arrays of rutile TiO2 composed of nanorods were fabricated on p-type (111)-oriented silicon substrates and, all substrates were seeded with a TiO2 seed layer synthesized by radio-frequency reactive magnetron sputtering system. Chemical bath deposition (CBD) was carried out to grow rutile TiO2 nanorods on Si substrate. Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses showed the tetragonal rutile structure of the synthesized TiO2 nanorods. Optical properties were examined by photoluminescence spectroscopy. The spectra exhibit one strong UV emission peak. Which can be seen at around 396 nm. In the visible region, TiO2 demonstrated two dominant PL emissions centered at around 528 and 705 nm. The experimental results showed that the CBD method enabled the formation of photosensitive, high-quality rutile TiO2 nanorods with few defects for humidity sensor and in future optoelectronic nanodevice applications.

Nanocrystalline CdS thin films were grown on Si(1 0 0) substrates using microwave-assisted chemical bath deposition. Aqueous solutions of cadmium chloride (CdCl2) and thiourea (TU) were used as cadmium (Cd+2) and sulfur (S−2) ion sources, respectively. Structural, morphological, and optical analyses showed that the quality of the grown CdS nanocrystalline thin films depends on the concentration of TU. The photoresponse of the devices made using such CdS films strongly depends on the TU concentration. The photodetector made of CdS films synthesized using 0.15 M exhibited high responsivity and exceptional sensitivity of 952 at an applied voltage of 1 V. Upon exposure to 460 nm-light pulses, a fast response time (∼10 ms) was achieved. The obtained results revealed that the photoresponse properties of CdS-based photodetectors could be markedly improved by controlling the molar concentration of TU.

The growth and characterization of a p–n heterojunction photodiode were studied. This photodiode was based on rutile TiO2 nanorods (NRs) grown on p-type (1 1 1)-oriented silicon substrate seeded with a TiO2 layer synthesized by radio-frequency (RF) reactive magnetron sputtering. Chemical bath deposition (CBD) was performed to grow rutile TiO2 NRs on Si substrate. The structural and optical properties of the sample were studied by X-ray diffraction (XRD) and field emission-scanning electron microscopy (FESEM) analyses. Results showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were further examined by photoluminescence spectroscopy, and a high-intensity UV peak centered at around 392 nm compared with visible defect peaks centered at 527 and 707 nm was observed. Upon exposure to 395 nm light (2.3 mW/cm) at five-bias voltage, the device showed 2.9 × 102 sensitivity. In addition, the internal gain of the photodiode was 3.92, and the photoresponse peak was 106 mA/W. Furthermore, the photocurrent was 3.06 × 10−4 A. The response and the recovery times were calculated to be 10.4 and 11 ms, respectively, upon illumination to a pulse UV light (405 nm, 0.22 mW/cm2) at five-bias voltage. All of these results demonstrate that this high-quality photodiode can be a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

The effects of pH on the structural, morphological and optical properties of TiO2 nanorods were investigated. Nanorods were fabricated on p-type (1 1 1)-oriented silicon substrates and all substrates were seeded with a TiO2 seed layer synthesized with a radio-frequency reactive magnetron sputtering system (the TiO2 seed layer was also examined in this research). Chemical bath deposition (CBD) was performed to grow rutile TiO2 nanorods on Si substrate at various pH values (0.5, 0.7 and 0.9). Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses showed the tetragonal rutile structure of the synthesized TiO2 nanorods. Optical properties were examined photoluminescence spectroscopy, which indicated a high-intensity UV peak centered at around 390 nm for all samples compared with visible defect peaks. Experimental results showed that the TiO2 nanorods grown at pH 0.7 exhibited the optimal structural properties. Moreover, the CBD method enabled the formation of photosensitive and high-quality rutile TiO2 nanorods with few defects for future optoelectronic nanodevice applications.

Effects of annealing treatment on growth of rutile TiO2 nanorods on structural, morphological and optical properties of TiO2 nanorods were investigated. The nanorods were fabricated on p-type (111)-oriented silicon substrates and, all substrates were seeded with a TiO2 seed layer synthesized by radio-frequency reactive magnetron sputtering system. Chemical bath deposition (CBD) was carried out to grow rutile TiO2 nanorods on Si substrate at different annealing temperatures (350, 550, 750, and 950 °C). Raman spectroscopy, X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) analyses showed the tetragonal rutile structure of the synthesized TiO2 nanorods. Optical properties were examined by photoluminescence spectroscopy. The spectra exhibit one strong UV emission peak which can be seen at around 390 nm for all of the samples. In the visible region, TiO2 demonstrated two dominant PL emissions centered at around 519 and 705 nm. The experimental results showed that the TiO2 nanorods annealed at 550 °C exhibited the optimal structural properties. Moreover, the CBD method enabled the formation of photosensitive, high-quality rutile TiO2 nanorods with few defects for future optoelectronic nanodevice applications.

Highly uniform nanocrystalline cadmium sulfide (CdS) thin films were successfully deposited on Si (1 1 1) substrates by microwave-assisted chemical bath deposition technique. Cadmium chloride (CdCl2) and thiourea [SC(NH2)2] precursors with different molar concentrations were used to prepare nanocrystalline CdS thin films. The effect of the molar concentration of reagents on the quality of the deposited thin films was investigated. Structural and morphological studies revealed that the quality of the grown CdS thin films was significantly affected by molar concentrations of reagents. Optimal thin film quality was utilized to fabricate a nanocrystalline CdS-based optical sensor. Current–voltage measurements (I–V) for the fabricated device showed significant sensing to low-power (0.3 mW/cm2) 500 nm light. The device exhibited high responsivity of 0.65 AW−1 at 3 V applied bias. Time response measurements showed rapid response and baseline recovery under low applied bias voltage, indicating good quality of the deposited thin film. A simple and low-cost method to fabricate a low-power, highly photosensitive optical sensor was introduced.

Nanocrystalline cadmium sulfide thin films were successfully grown on Si(100) substrates using microwaveassisted chemical bath deposition technique. Aqueous solutions of cadmium chloride (CdCl2) and thiourea [SC(NH2)2] were used as cadmium Cd+2 and sulfur S -2 ions sources, respectively to prepare nanocrystalline CdS thin films. The effect of reagents molar concentration on the quality of the prepared CdS thin films was investigated. Analysis revealed that using the chemical bath deposition technique aided by microwave irradiation good quality nanocrystalline CdS thin films can be grown on Si substrates by relatively short deposition time. Simple and cost effective way was introduced to synthesis nanocrystalline CdS thin films on Si substrates that would have potential application prospects in optoelectronic applications.

A self-powered highly photosensitive photodetector based on a nanocrystalline CdS thin film was fabricated using a microwave-assisted chemical bath deposition. In this study, highly uniform nanocrystalline CdS thin films were grown on Si(1 0 0) substrates from aqueous solutions of cadmium chloride (CdCl2) and thiourea [SC(NH2)2], which served as cadmium Cd2+ and sulfur S2- ions sources, respectively. Structural, morphological and optical analysis revealed that good-quality nanocrystalline CdS thin films were synthesized. Current-voltage (I-V) measurements of the fabricated photodetector showed a significant sensitivity to visible light at zero applied voltage, indicating that the fabricated device is a self-powered photodetector. The device was highly photosensitive to low-power visible light; it showed a sensitivity of 97.2 × 103 to (1.20 mW/cm2) 500-nm light, without an external bias. Photoresponse measurements demonstrated the highly reproducible characteristics of the fabricated photodetector with rapid response and baseline recovery time. This work introduces a simple and low-cost method for fabricating a rapid-response, highly photosensitive photodetector with zero power consumption. The mechanism of self-powered photodetectors is discussed.

Rutile titanium dioxide (TiO2) nanostructures were successfully fabricated using the simple chemical bath deposition method at various deposition temperatures. These nanostructures were fabricated on (100 ± 10 nm) TiO2 seed layer coated glass, which was prepared via radio frequency (RF) magnetron sputtering at a substrate temperature of 350 °C. The synthesized TiO2 nanostructures were annealed at 550 °C for 2 h and examined via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), and Raman spectroscopy. The XRD patterns showed the presence of the peaks characteristic of rutile phase. The band gap of the TiO2 nanostructures was calculated using the UV–vis absorption spectrum and was determined to be between 3.15 and 3.24 eV. The Raman spectra contained three characteristic bands at 232, 446 and 612 cm−1, which correspond to the tetragonal TiO2 rutile. The results showed good quality of nanocrystalline TiO2 rutile phase.

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