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Controlled-growth of ZnO nanowires with different processing temperature

Yap CC, Muhammad Yahaya, Muhamad Mat Salleh, Dee CF

Sains Malaysiana, 2008;37:233-237.

ZnO nanowires have been synthesized using a catalyst-free carbothermal reduction approach on SiO2-coated Si substrates in a flowing nitrogen atmosphere with a mixture of ZnO and graphite as reactants. The collected ZnO nanowires have been characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and photoluminescence spectroscopy. Controlled growth of the ZnO nanowires was achieved by manipulating the reactants heating temperature from 700 to 1000 oC. It was found that the optimum temperature to synthesize high density and long ZnO nanowires was about 800 0C. The possible growth mechanism of ZnO nanowires is also proposed.

Matched MeSH terms: Zinc Oxide
Prevention of coronal discoloration induced by root canal sealer remnants using Dentin Bonding agent: An in vitro study

Khim TP, Sanggar V, Shan TW, Peng KC, Western JS, Dicksit DD

J Conserv Dent, 2018 10 9;21(5):562-568.
PMID: 30294122 DOI: 10.4103/JCD.JCD_115_18

Introduction: Among the various causes of tooth discoloration after root canal treatment, percolation of sealer remnants into the dentinal tubules of the pulp chamber is the most common cause.
Objectives: The aim of this study is to evaluate the efficacy of dentin bonding agent (DBA) in preventing coronal discoloration caused by four different root canal sealers- MTA Fillapex, Sealapex, Zical and Z. O. B seal at different time intervals by measuring chromatic alterations using digital images analysis method.
Methodology: Ninety mandibular premolars were collected and sectioned at 1 mm below the cementoenamel junction. Standard access cavity preparations of dimensions (depth-3 mm, width-0.8 mm, and length-3 mm) were prepared with a No. 245 bur through the cervical access. Following the standard irrigation protocol, specimens were then randomly divided into nine groups (four groups without DBA [1-4] +4 groups with DBA [5-8] +1 negative control [9]). In Groups 1-4, four different root canal sealers (MTA Fillapex, Sealapex, Zical, and Z.O.B seal) were applied to the walls of the pulp chamber. For Groups 5-8, the samples were etched with 37% phosphoric acid and DBA application was done before the respective root canal sealer application. The cervical access in all specimens was sealed using glass ionomer cement. Digital photographs were taken under standard lighting and environmental conditions at different time intervals: preprocedural, postprocedural, and after 1, 2, 3, and 4 months. These images were analyzed using Adobe Photoshop CS6 from which laboratory values and subsequently Delta E values were obtained.
Results: Statistical analysis performed using repeated measures ANOVA and post hoc Tukey's tests show that the groups with DBA application had significantly lower mean Delta E values (P < 0.05) compared to the groups without DBA application.
Conclusion: DBAs applied to the dentinal walls of the pulp chamber before obturation can effectively reduce the sealer-induced coronal discoloration.

Matched MeSH terms: Zinc Oxide-Eugenol Cement
Fulltext SOLAR PHOTOCATALYTIC EFFICIENCY OF ZINC OXIDE FOR WATER DECONTAMINATION

FARAH EILYANA MOHAMED

UMT Journal of Undergraduate Research, 2019;1(1):92-102.
MyJurnal

Solar photocatalysis is a green technology that takes advantage of sustainable solar energy for enhancing oxidation process of numerous harmful water contaminants. In this study, a custom solar driven zinc oxide (ZnO)-mediated photocatalytic system was developed and its efficiency to remove organic contaminants as well as to disinfect selected bacteria was investigated. Methylene blue (MB) dye was used as the model organic contaminant, while Escherichia coli(E.coli) was used as the model fecal coliform bacteria in contaminated water. A series of photodegradation experiments were conducted on water contaminated with either 10 mg/L of MB or ~1010CFU/ml of E.coli. The experiments were completed under sunlight irradiation in the presence of 1 g/L of nano ZnO photocatalyst for up to 6 hours. Using a solar thermal collector, the photoreactor operated in the temperature range of 25 to 50 oC. The findings revealed that the combination of solar thermal with solar photocatalysis usingZnO intensified the degradation of MB and disinfection of E.coli. 98.08% of MB dye and 99.99% of E.coliwere successfully removed from the water within the first 3 hours of treatment. Almost complete removal was eventually achieved after 6 hours of treatment. It is therefore suggested that ZnO-based solar photocatalytic system developed in this study is highly efficient at enhancing water decontamination process.

Matched MeSH terms: Zinc Oxide
Co-synthesis and characterization of In2O3 and ZnO nanowires

Abrar Ismardi, Chang FD, Hamzah A, Bais B, Salleh M, Majlis B, et al.

Sains Malaysiana, 2012;41:459-463.

Co-synthesis of In2O3 and ZnO nanowires (NWs) were grown on silicon and alumina substrates using vapour transport deposition method. Their morphological structures showed that the NWs were rather aligned on silicon substrate and randomly oriented on alumina substrate. The formation of NWs on silicon substrate was found to be dominated by the growth of ZnO NWs while that on alumina substrate was dominated by the growth of In2O3 NWs. The In2O3 and ZnO NWs were highly crystalline and have wurtzite structure.

Matched MeSH terms: Zinc Oxide
Fulltext A facile thermal-treatment route to synthesize ZnO nanosheets and effect of calcination temperature

Al-Hada NM, Saion EB, Shaari AH, Kamarudin MA, Flaifel MH, Ahmad SH, et al.

PLoS One, 2014;9(8):e103134.
PMID: 25093752 DOI: 10.1371/journal.pone.0103134

A facile thermal-treatment route was successfully used to synthesize ZnO nanosheets. Morphological, structural, and optical properties of obtained nanoparticles at different calcination temperatures were studied using various techniques. The FTIR, XRD, EDX, SEM and TEM images confirmed the formation of ZnO nanosheets through calcination in the temperature between 500 to 650 °C. The SEM images showed a morphological structure of ZnO nanosheets, which inclined to crumble at higher calcination temperatures. The XRD and FTIR spectra revealed that the samples were amorphous at 30 °C but transformed into a crystalline structure during calcination process. The average particle size and degree of crystallinity increased with increasing calcination temperature. The estimated average particle sizes from TEM images were about 23 and 38 nm for the lowest and highest calcination temperature i.e. 500 and 650 °C, respectively. The optical properties were determined by UV-Vis reflection spectrophotometer and showed a decrease in the band gap with increasing calcination temperature.

Matched MeSH terms: Zinc Oxide/chemistry*
Fulltext Synthesis mechanism of low-voltage praseodymium oxide doped zinc oxide varistor ceramics prepared through modified citrate gel coating

Abdullah WR, Zakaria A, Ghazali MS

Int J Mol Sci, 2012;13(4):5278-89.
PMID: 22606043 DOI: 10.3390/ijms13045278

High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr(6)O(11)) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr(6)O(11) addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr(6)O(11) from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr(6)O(11) content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

Matched MeSH terms: Zinc Oxide/chemistry*
Fulltext Effect of ZnO on the physical properties and optical band gap of soda lime silicate glass

Zaid MH, Matori KA, Aziz SH, Zakaria A, Ghazali MS

Int J Mol Sci, 2012;13(6):7550-8.
PMID: 22837711 DOI: 10.3390/ijms13067550

This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased.

Matched MeSH terms: Zinc Oxide/chemistry*
Fulltext Photopyroelectric spectroscopic studies of ZnO-MnO(2)-Co(3)O(4)-V(2)O(5) ceramics

Rizwan Z, Zakaria A, Ghazali MS

Int J Mol Sci, 2011;12(3):1625-32.
PMID: 21673911 DOI: 10.3390/ijms12031625

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO(2) + 0.4Co(3)O(4) + xV(2)O(5)), x = 0-1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300-800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (E(g)) was 2.11 eV for 0.3 mol% V(2)O(5) at a sintering temperature of 1025 °C as determined from the plot (ρhυ)(2)versushυ. With a further increase in V(2)O(5), the value of E(g) was found to be 2.59 eV. Steepness factor 'σ(A)' and 'σ(B)', which characterize the slope of exponential optical absorption, is discussed with reference to the variation of E(g). XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively.

Matched MeSH terms: Zinc Oxide/chemistry*
Effects of the nitric acid concentrations on the etching process, structural and optical properties of porous zinc oxide thin films

C.G. Ching, Leonard Lu, C.I. Ang, P.K. Ooi, S.S. Ng, Z. Hassan, et al.

Sains Malaysiana, 2013;42:1327-1332.

The present study reports on the fabrication of porous zinc oxide by wet chemical etching. ZnO thin films were deposited via radio-frequency magnetron sputtering on p-type silicon with (111) preferred orientation. The etchants used in the present work were 0.1% and 1.0% nitric acid (HNO3) solutions. ZnO were etched at various times and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy to allow the examination of their structural and optical properties. The XRD results revealed that the intensity of ZnO(002) decreased when the thin films were etched in varying HNO3 concentrations over different periods of time. The above observation is attributed to the dissolution of the ZnO(002). The SEM images showed that the thickness of the ZnO layers decreased over the etching time, which resulted from the isotropic etching by the HNO3 solution. The PL emission intensity initially increased with increasing etching time. However, with further etching of the samples, the PL spectra showed a decreasing trend in intensity as a result of the decrease in the surface-to-volume ratio. All results lead to the conclusion that 1.0% HNO3 has the capability to change the ZnO surface significantly.

Matched MeSH terms: Zinc Oxide
Fulltext Development of antiproliferative nanohybrid compound with controlled release property using ellagic acid as the active agent

Hussein MZ, Al Ali SH, Zainal Z, Hakim MN

Int J Nanomedicine, 2011;6:1373-83.
PMID: 21796241 DOI: 10.2147/IJN.S21567

An ellagic acid (EA)-zinc layered hydroxide (ZLH) nanohybrid (EAN) was synthesized under a nonaqueous environment using EA and zinc oxide (ZnO) as the precursors. Powder X-ray diffraction showed that the basal spacing of the nanohybrid was 10.4 Å, resulting in the spatial orientation of EA molecules between the interlayers of 22.5° from z-axis with two negative charges at 8,8' position of the molecules pointed toward the ZLH interlayers. FTIR study showed that the intercalated EA spectral feature is generally similar to that of EA, but with bands slightly shifted. This indicates that some chemical bonding of EA presence between the nanohybrid interlayers was slightly changed, due to the formation of host-guest interaction. The nanohybrid is of mesopores type with 58.8% drug loading and enhanced thermal stability. The release of the drug active, EA from the nanohybrid was found to be sustained and therefore has good potential to be used as a drug controlled-release formulation. In vitro bioassay study showed that the EAN has a mild effect on the hepatocytes cells, similar to its counterpart, free EA.

Matched MeSH terms: Zinc Oxide/chemistry*
Fulltext Simple Response Surface Methodology: Investigation on Advance Photocatalytic Oxidation of 4-Chlorophenoxyacetic Acid Using UV-Active ZnO Photocatalyst

Lee KM, Hamid SBA

Materials (Basel), 2015 Jan 19;8(1):339-354.
PMID: 28787941 DOI: 10.3390/ma8010339

The performance of advance photocatalytic degradation of 4-chlorophenoxyacetic acid (4-CPA) strongly depends on photocatalyst dosage, initial concentration and initial pH. In the present study, a simple response surface methodology (RSM) was applied to investigate the interaction between these three independent factors. Thus, the photocatalytic degradation of 4-CPA in aqueous medium assisted by ultraviolet-active ZnO photocatalyst was systematically investigated. This study aims to determine the optimum processing parameters to maximize 4-CPA degradation. Based on the results obtained, it was found that a maximum of 91% of 4-CPA was successfully degraded under optimal conditions (0.02 g ZnO dosage, 20.00 mg/L of 4-CPA and pH 7.71). All the experimental data showed good agreement with the predicted results obtained from statistical analysis.

Matched MeSH terms: Zinc Oxide
Fulltext Perceptions of students in different phases of medical education of the educational environment: Universiti Sultan Zainal Abidin

Rahman NI, Aziz AA, Zulkifli Z, Haj MA, Mohd Nasir FH, Pergalathan S, et al.

Adv Med Educ Pract, 2015;6:211-22.
PMID: 25848333 DOI: 10.2147/AMEP.S78838

The Dundee Ready Education Environment Measure (DREEM) was planned and designed to quantify the educational environment precisely for medical schools and health-related professional schools. DREEM is now considered a valid and reliable tool, which is globally accepted for measuring the medical educational environment. The educational environment encountered by students has an impact on satisfaction with the course of study, perceived sense of well-being, aspirations, and academic achievement. In addition to being measurable, the educational environment can also be changed, thus enhancing the quality of medical education and the environment, and the medical education process. The objective of this study was to assess the educational environment of the Universiti Sultan Zainal Abidin (UniSZA) undergraduate medical program from the students' perspective. The study expected to explore UniSZA medical students' overall perceptions, perceptions of learning, teachers, atmosphere, academic self-perception, and social self-perception using the DREEM questionnaire.

Matched MeSH terms: Zinc Oxide
Fulltext Preparation and Evaluation of the ZnO NP-Ampicillin/Sulbactam Nanoantibiotic: Optimization of Formulation Variables Using RSM Coupled GA Method and Antibacterial Activities

Sharma N, Singh V, Pandey AK, Mishra BN, Kulsoom M, Dasgupta N, et al.

Biomolecules, 2019 11 21;9(12).
PMID: 31766572 DOI: 10.3390/biom9120764

Nanoparticles (NPs) possessing antibacterial activity represent an effective way of overcoming bacterial resistance. In the present work, we report a novel formulation of a nanoantibiotic formed using Ampicillin/sulbactam (Ams) and a zinc oxide nanoparticle (ZnO NP). 'ZnO NP-Ams' nanoantibiotic formulation is optimized using response surface methodology coupled genetic algorithm approach. The optimized formulation of nanoantibiotic (ZnO NP: 49.9 μg/mL; Ams: 33.6 μg/mL; incubation time: 27 h) demonstrated 15% enhanced activity compared to the unoptimized formulation against K. pneumoniae. The reactive oxygen species (ROS) generation was directly proportional to the interaction time of nanoantibiotic and K. pneumoniae after the initial lag phase of ~18 h as evident from 2'-7'-Dichlorodihydrofluorescein diacetate assay. A low minimum inhibitory concentration (6.25 μg/mL) of nanoantibiotic formulation reveals that even a low concentration of nanoantibiotic can prove to be effective against K. pneumoniae. The importance of nanoantibiotic formulation is also evident by the fact that the 100 μg/mL of Ams and 25 µg of ZnO NP was required individually to inhibit the growth of K. pneumonia, whereas only 6.25 μg/mL of optimized nanoantibiotic formulation (ZnO NP and Ams in the ratio of 49.9: 33.6 in μg/mL and conjugation time of 27 h) was needed for the same.

Matched MeSH terms: Zinc Oxide/pharmacology*
Fulltext Compositions and antimicrobial properties of binary ZnO-CuO nanocomposites encapsulated calcium and carbon from Calotropis gigantea targeted for skin pathogens

Govindasamy GA, Mydin RBSMN, Sreekantan S, Harun NH

Sci Rep, 2021 01 08;11(1):99.
PMID: 33420110 DOI: 10.1038/s41598-020-79547-w

Calotropis gigantea (C. gigantea) extract with an ecofriendly nanotechnology approach could provide promising antimicrobial activity against skin pathogens. This study investigates the antimicrobial capability of green synthesized binary ZnO-CuO nanocomposites from C. gigantea against non-MDR (Staphylococcus aureus and Escherichia coli) and MDR (Klebsiella pneumoniae, Pseudomonas aeruginosa and methicillin-resistant S. aureus) skin pathogens. Scanning electron microscopy and transmission electron microscopy revealed the size and shape of B3Z1C sample. Results of X-ray powder diffraction, energy-dispersive spectroscopy, FTIR and UV-Vis spectroscopy analyses confirmed the presence of mixed nanoparticles (i.e., zinc oxide, copper oxide, carbon and calcium) and the stabilising phytochemical agents of plant (i.e., phenol and carbonyl). Antimicrobial results showed that carbon and calcium decorated binary ZnO-CuO nanocomposites with compositions of 75 wt% of ZnO and 25 wt% CuO (B3Z1C) was a strong bactericidal agent with the MBC/MIC ratio of ≤ 4 and ≤ 2 for non-MDR and MDR pathogens, respectively. A significant non-MDR zone of inhibitions were observed for BZC by Kirby-Bauer disc-diffusion test. Further time-kill observation revealed significant fourfold reduction in non-MDR pathogen viable count after 12 h study period. Further molecular studies are needed to explain the biocidal mechanism underlying B3Z1C potential.

Matched MeSH terms: Zinc Oxide/pharmacology*; Zinc Oxide/chemistry*
Fulltext Zinc oxide from aloe vera extract: two-level factorial screening of biosynthesis parameters

Rasli NI, Basri H, Harun Z

Heliyon, 2020 Jan;6(1):e03156.
PMID: 32042952 DOI: 10.1016/j.heliyon.2020.e03156

Zinc oxide (ZnO) was biosynthesised from aloe vera plant extract. The aloe vera plant extract was used as a reducing agent in biosynthesis process. Green synthesis method was proposed because it is cost effective and environmentally friendly. ZnO was characterised using SEM, EDX, FTIR, and XRD analyses. The antibacterial property was tested against Escherichia coli. The effects of aloe vera volume (2-50) mL, precursor concentration (0.001-0.300) M, reaction time (20 min-48 h), and temperature of the reaction (26-200) °C on ZnO characteristics were investigated and screened using a two-level factorial method. Based on the observation and ANOVA analysis result, precursor concentration was the only significant parameter that affected the production of the ZnO nanoparticles (NPs). The EDX analysis proved the presence of ZnO while the SEM analysis confirmed the average size of ZnO particle size was in the range of (18-618) μm with a rod-shape appearance. The XRD analysis showed that the average crystallite size was 0.452 μm and it was in the hexagonal phase. It was also proven to have antibacterial property against E. coli.

Matched MeSH terms: Zinc Oxide
Fulltext Gas sensors based on one dimensional nanostructured metal-oxides: a review

Arafat MM, Dinan B, Akbar SA, Haseeb AS

Sensors (Basel), 2012;12(6):7207-58.
PMID: 22969344 DOI: 10.3390/s120607207

Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO(2), TiO(2), In(2)O(3), WO(x), AgVO(3), CdO, MoO(3), CuO, TeO(2) and Fe(2)O(3). Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

Matched MeSH terms: Zinc Oxide
Fulltext Seed/catalyst-free vertical growth of high-density electrodeposited zinc oxide nanostructures on a single-layer graphene

Aziz NS, Mahmood MR, Yasui K, Hashim AM

Nanoscale Res Lett, 2014 Feb 26;9(1):95.
PMID: 24568668 DOI: 10.1186/1556-276X-9-95

We report the seed/catalyst-free vertical growth of high-density electrodeposited ZnO nanostructures on a single-layer graphene. The absence of hexamethylenetetramine (HMTA) and heat has resulted in the formation of nanoflake-like ZnO structure. The results show that HMTA and heat are needed to promote the formation of hexagonal ZnO nanostructures. The applied current density plays important role in inducing the growth of ZnO on graphene as well as in controlling the shape, size, and density of ZnO nanostructures. High density of vertically aligned ZnO nanorods comparable to other methods was obtained. The quality of the ZnO nanostructures also depended strongly on the applied current density. The growth mechanism was proposed. According to the growth timing chart, the growth seems to involve two stages which are the formation of ZnO nucleation and the enhancement of the vertical growth of nanorods. ZnO/graphene hybrid structure provides several potential applications in electronics and optoelectronics such as photovoltaic devices, sensing devices, optical devices, and photodetectors.

Matched MeSH terms: Zinc Oxide
Distinguishing normal and aggregated alpha-synuclein interaction on gold nanorod incorporated zinc oxide nanocomposite by electrochemical technique

Adam H, Gopinath SCB, Arshad MKM, Parmin NA, Hashim U

Int J Biol Macromol, 2021 Feb 28;171:217-224.
PMID: 33418041 DOI: 10.1016/j.ijbiomac.2021.01.014

Misfolding and accumulation of the protein alpha synuclein in the brain cells characterize Parkinson's disease (PD). Electrochemical based aluminum interdigitated electrodes (ALIDEs) was fabricated by using conventional photolithography method and modified the surfaces with zinc oxide and gold nanorod by using spin coating method for the analysis of PD protein biomarker. The device surface modified with gold nanorod of 25 nm diameter was used. The bare devices and the surface modified devices were characterized by Scanning Electron Microscope, 3D-Profilometer, Atomic Force Microscope and high-power microscope. The above measurement was also performed to measure the interaction of antibody with aggregated alpha-synuclein for normal, aggregated and aggregated alpha synuclein in human serum and distinguished against 3 control proteins (PARK1, DJ-1 and Factor IX). The detection limit for normal alpha synuclein was 1 f. with the sensitivity of 1 f. on a linear regression (R2 = 0.9759). The detection limit for aggregated alpha synuclein was 10 aM with the sensitivity of 1 aM on a linear regression (R2 = 0.9797). Also, the detection limit of aggregated alpha synuclein in serum was 10 aM with the sensitivity of 1 aM on a linear regression (R2 = 0.9739). These results however indicate that, serum has only minimal amount of alpha synuclein.

Matched MeSH terms: Zinc Oxide
Fulltext Determination of acceptor concentration, depletion width, donor level movement and sensitivity factor of ZnO on diamond heterojunction under UV illumination

Saw KG, Tneh SS, Yam FK, Ng SS, Hassan Z

PLoS One, 2014;9(2):e89348.
PMID: 24586707 DOI: 10.1371/journal.pone.0089348

The concentration of acceptor carriers, depletion width, magnitude of donor level movement as well as the sensitivity factor are determined from the UV response of a heterojunction consisting of ZnO on type IIb diamond. From the comparison of the I-V measurements in dark condition and under UV illumination we show that the acceptor concentration (∼10(17) cm(-3)) can be estimated from p-n junction properties. The depletion width of the heterojunction is calculated and is shown to extend farther into the ZnO region in dark condition. Under UV illumination, the depletion width shrinks but penetrates both materials equally. The ultraviolet illumination causes the donor level to move closer to the conduction band by about 50 meV suggesting that band bending is reduced to allow more electrons to flow from the intrinsically n-type ZnO. The sensitivity factor of the device calculated from the change of threshold voltages, the ratio of dark and photocurrents and identity factor is consistent with experimental data.

Matched MeSH terms: Zinc Oxide/chemistry*
Fulltext Ohmic-rectifying conversion of Ni contacts on ZnO and the possible determination of ZnO thin film surface polarity

Saw KG, Tneh SS, Tan GL, Yam FK, Ng SS, Hassan Z

PLoS One, 2014;9(1):e86544.
PMID: 24466144 DOI: 10.1371/journal.pone.0086544

The current-voltage characteristics of Ni contacts with the surfaces of ZnO thin films as well as single crystal (0001) ZnO substrate are investigated. The ZnO thin film shows a conversion from Ohmic to rectifying behavior when annealed at 800°C. Similar findings are also found on the Zn-polar surface of (0001) ZnO. The O-polar surface, however, only shows Ohmic behavior before and after annealing. The rectifying behavior observed on the Zn-polar and ZnO thin film surfaces is associated with the formation of nickel zinc oxide (Ni1-xZnxO, where x = 0.1, 0.2). The current-voltage characteristics suggest that a p-n junction is formed by Ni1-xZnxO (which is believed to be p-type) and ZnO (which is intrinsically n-type). The rectifying behavior for the ZnO thin film as a result of annealing suggests that its surface is Zn-terminated. Current-voltage measurements could possibly be used to determine the surface polarity of ZnO thin films.

Matched MeSH terms: Zinc Oxide/chemistry*

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