Al-, Ga-, and In-doped ZnO thin films via aerosol assisted CVD for use as transparent conducting oxides

Al-, Ga-, and In-doped ZnO thin films were deposited on glass substrates by aerosol assisted chemical vapour deposition (AACVD) at a deposition temperature of 450 °C. The air-stable compound zinc acetylacetonate [Zn(acac)2] was used as a Zn source, whilst for the dopants of Al, Ga and In, the corresponding trichloride was used. Methanol solutions of the metal salts were used as precursor solutions and N2 carrier gas was used for the aerosol. Films were grown in approximately 30 min and were synthesised using dopant values of 5, 10, 15 and 20 mol.% (with respect to the Zn) in the precursor solution. XRD analysis showed that the films were wurtzite ZnO. XPS analysis confirmed the presence of the dopants in the films. Several of the films showed high transparency (>80%) in the visible range, and low resistivity (∼10−3 Ω cm)

Scaling aerosol assisted chemical vapour deposition: Exploring the relationship between growth rate and film properties

Thin films of fluorine doped tin oxide were deposited, by an aerosol assisted chemical vapour deposition route, to study the effect of scaling the growth rate. The effect of precursor concentration on the growth rate of the films and the properties of deposited films were compared. The films were characterised by X-ray diffraction, scanning electron microscopy, UV/vis spectroscopy, X-ray photoelectron spectroscopy and Hall effect measurements. A maximum film growth rate of ca. 100 nm min− 1 was observed, which is significantly faster than previously reported aerosol assisted studies. This method shows the ability of aerosol assisted methods to deliver high growth rates whilst maintaining the ease of doping and control over stoichiometry

The Effect of Solvent on Al-doped ZnO Thin Films Deposited via Aerosol Assisted CVD

Aluminium-doped zinc oxide (AZO) thin films were deposited via aerosol assisted chemical vapour deposition (AACVD) from zinc acetylacetonate and aluminium chloride at 450 °C. The precursor solutions consisted of methanol in a mixture with one other secondary solvent, including toluene, tetrahydrofuran, n-hexane, cyclohexane, and ethyl acetate. The crystal structures, elemental compositions and surface morphologies of the resulting AZO films were determined, as well as the optoelectronic properties. It was found that the more polar solvents enhanced growth in the (002) plane of the wurtzite crystal structure, and that solutions with low viscosities resulted in superior grain growth. The film deposited from a solution consisting of methanol and ethyl acetate displayed the lowest visible transmittance, due to carbon contamination. However, it also exhibited 60% lower resistivity, in comparison to the film deposited using methanol only. This suggests that optoelectronic properties can be tuned for specific photovoltaic devices

Microwave-Assisted Synthesis and Processing of Al-Doped, Ga-Doped, and Al, Ga Codoped ZnO for the Pursuit of Optimal Conductivity for Transparent Conducting Film Fabrication

This work reports the microwave-assisted fabrication of highly conducting Al-doped ZnO (AZO), Ga-doped ZnO (GZO), and Al, Ga codoped ZnO (AGZO) materials as cheaper earth abundant alternatives to indium tin oxide (ITO) for transparent conducting applications. All three doped ZnO powder samples were compressed into pellets, and their electrical properties were evaluated after the postsynthesis heat treatment. The heat treatment was performed by sintering the pellets at 600 °C in a reducing atmosphere using either conventional radiant annealing for 3 h or microwave annealing for 90 s. The Al and Ga dopant levels were systematically varied from 0.5 to 2.5 at. %, and it was found that the lowest resistivity values for the pelleted singly doped ZnO powders exist when the doping level is adjusted to 1.5 at. % for both AZO and GZO, giving resistivity values of 4.4 × 10–3 and 4.3 × 10–3 Ω·cm, respectively. The lowest resistivity of 5.6 × 10–4 Ω·cm was achieved for the pelleted codoped AGZO powder using the optimized Al and Ga dopant levels. Notably, this value is one magnitude lower than the best literature reported value for conventionally synthesized codoped AGZO powder. The resistivity values obtained for the pellets after radiant and microwave postsynthesis heat treatment are comparable, although the microwave heat treatment was performed only for 90 s, compared to 3 h for conventional radiant heat treatment. Hence, significant gains were made in the postannealing step by reducing time, cost, and energy required, benefiting our thrust for finding sustainable routes toward alternative low-cost transparent conducting oxides. As a proof of concept, transparent conducting thin films were fabricated via a simple aerosol-assisted deposition technique using our best conducting AGZO nanoparticles. The films exhibited a visible transmittance as good as 90% and a resistivity of 5.7 × 10–3 Ω·cm, which can compete with the existing high cost ITO films

Transparent conducting oxide thin films of Si-doped ZnO prepared by aerosol assisted CVD

For the first time, aerosol assisted chemical vapour deposition (AACVD) was used to deposit Si-doped ZnO thin films on glass. Depositions were done at a temperature of 450 °C. The precursor solution was made by dissolving the air-stable compounds zinc acetylacetonate and tetraethyl orthosilicate in methanol with a small addition of acetic acid to aid solubility. The dopant concentration in the precursor solution was optimised to find the best optoelectronic properties. The incorporation of Si into the ZnO lattice was confirmed by unit cell volumes calculated from X-ray diffraction (XRD) data and by X-ray photoelectron spectroscopy (XPS). The films consisted of pure phase wurtzite ZnO, with preferred orientation in the (002) plane. Scanning electron microscopy (SEM) was used to examine the surface morphology of the films. The optical properties of the films were analysed using UV/vis spectroscopy and indicated that the average transmittance in the visible part of the spectrum (400-700 nm) varied between 72% and 80%. The electrical properties of the films were obtained from Hall effect measurements using the van der Pauw method. The incorporation of Si into the films resulted in a decrease in resistivity down to a minimum value of 2.0 × 10−2 Ω cm for the film deposited from a 4 mol% Si : Zn ratio in the precursor solution. This conductive film was a significant improvement over the non-conductive undoped ZnO film

Phosphorus doped SnO2 thin films for transparent conducting oxide applications: synthesis, optoelectronic properties and computational models

Phosphorus doped tin(iv) oxide (P:SnO2) films have been synthesised by an aerosol assisted chemical vapour deposition route. Triethyl phosphate was used as the phosphorus dopant source. The phosphorus concentration in solution was found to be key to electrical properties, with concentrations between 0.25-0.5 mol% phosphorus giving the lowest resistivities of the deposited films. The conductivity of the films synthesised improved on doping SnO2 with phosphorus, with resistivity values of 7.27 × 10-4 Ω cm and sheet resistance values of 18.2 Ω □-1 achieved for the most conductive films. Phosphorus doping up to 1.0 mol% was shown to improve visible light transmission of the deposited films. The phosphorus doping also had a significant effect on film morphology, with varying microstructures achieved. The films were characterised by X-ray diffraction, scanning electron microscopy, UV/vis spectroscopy, Hall effect measurements and X-ray photoelectron spectroscopy. The data generated was used to build computational models of phosphorus as a dopant for SnO2, showing that the phosphorus acts as a shallow one-electron n-type donor allowing for good conductivities. Phosphorus does not suffer from self-compensation issues associated with other dopants, such as fluorine

The health system impact of false positive newborn screening results for medium-chain acyl-CoA dehydrogenase deficiency: A cohort study

Background - There is no consensus in the literature regarding the impact of false positive newborn screening results on early health care utilization patterns. We evaluated the impact of false positive newborn screening results for medium-chain acyl-CoA dehydrogenase deficiency (MCADD) in a cohort of Ontario infants. Methods - The cohort included all children who received newborn screening in Ontario between April 1, 2006 and March 31, 2010. Newborn screening and diagnostic confirmation results were linked to province-wide health care administrative datasets covering physician visits, emergency department visits, and inpatient hospitalizations, to determine health service utilization from April 1, 2006 through March 31, 2012. Incidence rate ratios (IRRs) were used to compare those with false positive results for MCADD to those with negative newborn screening results, stratified by age at service use. Results - We identified 43 infants with a false positive newborn screening result for MCADD during the study period. These infants experienced significantly higher rates of physician visits (IRR: 1.42) and hospitalizations (IRR: 2.32) in the first year of life relative to a screen negative cohort in adjusted analyses. Differences in health services use were not observed after the first year of life. Conclusions - The higher use of some health services among false positive infants during the first year of life may be explained by a psychosocial impact of false positive results on parental perceptions of infant health, and/or by differences in underlying health status. Understanding the impact of false positive newborn screening results can help to inform newborn screening programs in designing support and education for families. This is particularly important as additional disorders are added to expanded screening panels, yielding important clinical benefits for affected children but also a higher frequency of false positive findings.This study was Funded through a Canadian Institutes of Health Research (CIHR) Emerging Team Grant (TR3-119195). Maria Karaceper received a graduate scholarship through a charitable donation to the Children’s Hospital of Eastern Ontario. This study was performed at the Institute for Clinical Evaluative Sciences (ICES), which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC)

Longer sleep is associated with lower BMI and favorable metabolic profiles in UK adults: Findings from the National Diet and Nutrition Survey

Ever more evidence associates short sleep with increased risk of metabolic diseases such as obesity, which may be related to a predisposition to non-homeostatic eating. Few studies have concurrently determined associations between sleep duration and objective measures of metabolic health as well as sleep duration and diet, however. We therefore analyzed associations between sleep duration, diet and metabolic health markers in UK adults, assessing associations between sleep duration and 1) adiposity, 2) selected metabolic health markers and 3) diet, using National Diet and Nutrition Survey data. Adults (n = 1,615, age 19–65 years, 57.1% female) completed questions about sleep duration and 3 to 4 days of food diaries. Blood pressure and waist circumference were recorded. Fasting blood lipids, glucose, glycated haemoglobin (HbA1c), thyroid hormones, and high-sensitivity C-reactive protein (CRP) were measured in a subset of participants. We used regression analyses to explore associations between sleep duration and outcomes. After adjustment for age, ethnicity, sex, smoking, and socioeconomic status, sleep duration was negatively associated with body mass index (-0.46 kg/m2 per hour, 95% CI -0.69 to -0.24 kg/m2, p < 0.001) and waist circumference (-0.9 cm per hour, 95% CI -1.5 to -0.3cm, p = 0.004), and positively associated with high-density lipoprotein cholesterol (0.03 mmol/L per hour, 95% CI 0.00 to 0.05, p = 0.03). Sleep duration tended to be positively associated with free thyroxine levels and negatively associated with HbA1c and CRP (p = 0.09 to 0.10). Contrary to our hypothesis, sleep duration was not associated with any dietary measures (p ≥ 0.14). Together, our findings show that short-sleeping UK adults are more likely to have obesity, a disease with many comorbidities

Methods for specifying the target difference in a randomised controlled trial : the Difference ELicitation in TriAls (DELTA) systematic review

Peer reviewedPublisher PD