Influence of Post-UV/Ozone Treatment of Ultrasonic-Sprayed Zirconium Oxide Dielectric Films for a Low-Temperature Oxide Thin Film Transistor

UID/CTM/50025/2019 PTDC/CTM-NAN/5172/2014 PTDC/NAN-MAT/32558/2017 project IUT194 ERC-StG-2014 GA 640598Solution-processed metal oxides require a great deal of thermal budget in order to achieve the desired film properties. Here, we show that the deposition temperature of sprayed zirconium oxide (ZrOx) thin film can be lowered by exposing the film surface to an ultraviolet (UV) ozone treatment at room temperature. Atomic force microscopy reveals a smooth and uniform film with the root mean square roughness reduced from ~ 0.63 nm (UVO-O) to ~ 0.28 nm (UVO-120) in the UV–ozone treated ZrOx films. X-ray photoelectron spectroscopy analysis indicates the formation of a Zr–O network on the surface film, and oxygen vacancy is reduced in the ZrOx lattice by increasing the UV–ozone treatment time. The leakage current density in Al/ZrOx/p-Si structure was reduced by three orders of magnitude by increasing the UV-ozone exposure time, while the capacitance was in the range 290–266 nF/cm2, corresponding to a relative permittivity (k) in the range 5.8–6.6 at 1 kHz. An indium gallium zinc oxide (IGZO)-based thin film transistor, employing a UV-treated ZrOx gate dielectric deposited at 200 °C, exhibits negligible hysteresis, an Ion/Ioff ratio of 104, a saturation mobility of 8.4 cm2 V−1S−1, a subthreshold slope of 0.21 V.dec−1, and a Von of 0.02 V. These results demonstrate the potentiality of low-temperature sprayed amorphous ZrOx to be applied as a dielectric in flexible and low-power-consumption oxide electronics.publishersversionpublishe

Application of ultrasonic sprayed zirconium oxide dielectric in zinc tin oxide-based thin film transistor

project IUT194 UID/CTM/50025/2019 project TK141 Grant Agreement 17161 SFRH/BD/116047/2016Solution processing of metal oxides has been the focal point of interest for many researchers mainly because of the cost effectiveness and improved properties of metal oxides. However, achieving uniform and high-quality film deposition has been a recurring challenge using various wet-chemical techniques. Herein, we report a fully solution-based fabrication process exploiting both the ultrasonic spray pyrolysis (USP) and spin coating techniques owing to their simplicity, high degree of freedom for mixing metal oxide precursor salt, and larger area deposition. An amorphous zirconium oxide (ZrOx) dielectric and zinc tin oxide (ZTO) semiconductor were deposited, respectively. The dielectric characteristics of the ZrOx thin films were accessed by fabricating MIS-devices for the samples deposited at 200 °C and 400 °C, which exhibited a capacitance of 0.35 and 0.67 μF cm−2 at 100 kHz and relative permittivity of 8.5 and 22.7, respectively. The ZrOx thin film was then integrated as the gate dielectric layer in ZTO solution-processed thin film transistors, exhibiting a high electrical performance with low hysteresis (−0.18 V), high on/off current ratio of 106 orders of magnitude, saturation mobility of 4.6 cm2 V s−1, subthreshold slope of 0.25 V dec−1, and operating at a low voltage window of 3 V. Based on these results, the as-fabricated ZTO/ZrOx TFT opens the potential application of solution-processed transistors for low-cost electronic devices.publishersversionpublishe

4.9% Efficient Sb2S3 Solar Cells from Semitransparent Absorbers with Fluorene-Based Thiophene-Terminated Hole Conductors

publishedVersio

Semitransparent Sb2S3 Thin Film Solar Cells by Ultrasonic Spray Pyrolysis for Use In Solar Windows

The integration of photovoltaic (PV) solar energy in zero-energy buildings requires durable and efficient solar windows composed of lightweight and semitransparent thin film solar cells. Inorganic materials with a high optical absorption coefficient, such as Sb2S3 (\u3e105 cm−1 at 450 nm), offer semitransparency, appreciable efficiency, and long-term durability at low cost. Oxide-free throughout the Sb2S3 layer thickness, as confirmed by combined studies of energy dispersive X-ray spectroscopy and synchrotron soft X-ray emission spectroscopy, semitransparent Sb2S3 thin films can be rapidly grown in air by the area-scalable ultrasonic spray pyrolysis method. Integrated into a ITO/TiO2/Sb2S3/P3HT/Au solar cell, a power conversion efficiency (PCE) of 5.5% at air mass 1.5 global (AM1.5G) is achieved, which is a record among spray-deposited Sb2S3 solar cells. An average visible transparency (AVT) of 26% of the back-contact-less ITO/TiO2/Sb2S3 solar cell stack in the wavelength range of 380–740 nm is attained by tuning the Sb2S3 absorber thickness to 100 nm. In scale-up from mm2 to cm2 areas, the Sb2S3 hybrid solar cells show a decrease in efficiency of only 3.2% for an 88 mm2 Sb2S3 solar cell, which retains 70% relative efficiency after one year of non-encapsulated storage. A cell with a PCE of 3.9% at 1 sun shows a PCE of 7.4% at 0.1 sun, attesting to the applicability of these solar cells for light harvesting under cloud cover

XPS

The data of oxygen (O1s) core level spectra of the surface of TiO2 films (Fig.5)

Degradation of MTBE

The data and calculations of the degradation of MTBE in the multi-section plug-flow photocatalytic reactor

Band gap Cal.

The raw data about band gap calculations of all samples (Fig.4b)

UV-VIS spectroscopy

Total transmittance spectra for TiO2 thin films (Fig.4a)