Wu Tang

Surface morphology modelling for the resistivity analysis of low temperature sputtered indium tin oxide thin films on polymer substrates

Amorphous or weakly crystalline indium tin oxide (ITO) thin film samples have been prepared on polymethylmethacrylate and polyethylene terephthalate substrates by RF-magnetron sputtering at a low substrate temperature. The surface morphological and electrical properties of the ITO layers were measured by atomic force microscopy (AFM) and a standard four-point probe measurement. The effect of surface morphology on the resistivity of ITO thin films was studied, which presented some different variations from crystalline films. Then, a simplified film system model, including the substrate, continuous ITO layer and ITO surface grain, was proposed to deal with these correlations. Based on this thin film model and the AFM images, a quadratic potential was introduced to simulate the characteristics of the ITO surface morphology, and the classical Kronig–Penney model, the semiconductor electrical theory and the modified Neugebauer–Webb model were used to expound the detailed experimental results. The modelling equation was highly in accord with the experimental variations of the resistivity on the characteristics of the surface morphology.

Energy band calculation of amorphous indium tin oxide films on polyethylene terephthalate substrate with indirect transition

Amorphous indium tin oxide films were grown on a polyethylene terephthalate substrate by RF-magnetron sputtering. The energy band, which contained not only the width of the optical band but also detailed information about the Fermi level (Ef) and mobility edge , was calculated according to the theory of amorphous semiconductors with the experimental parameters of transmittance and electrical conductivity. Furthermore, the calculated energy band can be used to effectively explain both the variation of electrical conductivity and the weak absorption at the wavelength range of 750–800 nm in our experiment. An indirect transition was also clearly observed in our samples during the calculation of the optical energy band.

The Microstructure, Resistivity and Infrared Emissivity of ITO Film with O/Ar Ratio Variation in Al2O3 Buffer Layer

ITO films with different oxygen-argon ratios varies from 0 % to 8 % for Al2O3 buffer layer have been fabricated by magnetron sputtering on soft PET substrate. The microstructure, resistivity, transmittance in visible light range and infrared emissivity were measured by XRD, four-point probe technology, UV-Vis spectrophotometer and Fourier Transform Infrared Spectroscopy (FTIR) as a function of different oxygen-argon ratios of Al2O3 buffer layers, respectively. It can be found that the (222) plane crystallization improves with the increase of O/Ar ratio, (622） peak under 2% O/Ar ratio and (440), (211) peaks under 8% O/Ar ratio appear, respectively. The resistivity is also influenced significantly by the O/Ar ratio, though the variation of resistivity is not sensitive to O/Ar ratio higher than 2%. The results reveal that the best ITO film performance under the oxygen-argon ratio 2% for Al2O3 buffer layer. It is also found that surface roughness and interface state play an important role in the variation of transmittance and emissivity. The emissivity of all the ITO films deposited on Al2O3 buffer layer is dominated by both sheet resistance and surface morphology.

Study on adhesion and electro-optical properties of ITO films on flexible PET substrate

Abstract High-quality ITO films on flexible PET substrate were prepared by RF magnetron sputtering at low deposition temperature with different Ar gas sputtering pressure. Adhesion and electro-optical properties of ITO films were investigated as a function of Ar partial pressure. The sputtering conditions provide very uniform ITO films with high transparency (> 85% in 400–760 nm spectra) and low electrical resistivity (1. 408 × 10 −3 −1.956 × 10 −3 Ω · cm). Scratch test experiments indicate that there is a good adhesion property between ITO films and PET substrate, the critical characteristic load increases from 16.5 to 23.2 N with increasing Ar sputtering pressure from 0.2 to 1.4 Pa.

Crystal Orientation and Hardness of Au/NiCr/Ta Films on Si-(111) Substrate Prepared by Magnetron Sputtering

Au/NiCr/Ta soft multi-layered metal films were deposited on hard Si-(111) substrate by magnetron sputtering. The crystal orientation, Hardness (H) and Elastic modulus (E) were investigated as a function of substrate temperature by XRD and nanoindentation techniques. The XRD revealed that all films on Si-(111) substrate are Au-(111) preferred orientation, indicating there are no alloying phases in the films, which is different from Au/NiCr/Ta films on Al2O3 substrate with a mixture of Au-(111) and Au-(200) orientation. Nanoindentation tests at shallow indentation depths (h≤t/4) where the hardness is reliable for metal films on hard substrate. Au film at substrate temperature 200°C has the highest hardness 4.2GPa. Meanwhile, the H/E value also indicated that the Au/NiCr/Ta films have preferable wear resistance at substrate temperature 200°C.

Microstructure and Resistivity of Low Temperature Deposition ITO Films on PET Substrate by Magnetron Sputtering

Sn doped indium oxide (ITO) films were fabricated on polyethylene terephtalate (PET) substrate by magnetron sputtering at low deposition temperature using a 10 wt % SnO2-doped In2O3 target applied in the infrared regions as low emissivity materials. The microstructure and surface morphology of ITO films was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM); the resistivity was investigated by four-point probe technology. It was found that the film with amorphous microstructure has highest resistivity to 1.956×10-3 2.cm at low deposition temperature and the surface roughness and resistivity increase with the increasing Ar sputtering pressure from 0.5Pa to 1.4Pa. The most interesting is that the resistivity increases with the increasing surface roughness, it indicates that there are internal correlation between roughness and resistivity.

Influence of Al2O3 Buffer Layers on the Properties of Indium–Tin Oxide Films on PET Substrate by RF-Magnetron Sputtering

Indium Tin Oxide (ITO) films on PET substrate sandwiching Al2O3 buffer layers with different thickness have been prepared by magnetron sputtering at low deposition temperature. The crystal structures, electrical and optical properties of ITO films have been investigated by XRD, four-point probe technology and UV-Vis spectrophotometer as a function of different Al2O3 buffer layers thickness, respectively. XRD reveals that there is an amorphous structure in ITO films with no buffer layer. However, ITO films became crystalline after sandwiching the buffer layer. It can be found that there are two major peaks, (222) and (400) of ITO film. A smallest resistivity of 3.53×10-4 Ω.cm was obtained for ITO film with Al2O3 buffer layers thickness 75nm. The average transmittance of ITO/Al2O3/PET films in the visible range of 400-760nm wavelength was around 80%. It can be conclude that the (222) orientation of ITO film is more in favor of low resistivity.

The Relationship between Residual Stress and Resistivity of Au/NiCr/Ta Multi-Layered Metallic Films by Magnetron Sputtering

Au/NiCr/Ta multi-layered metallic films were deposited on Al2O3 substrate by magnetron sputtering at different substrate temperature. The effect of substrate temperature on magnetron sputtering Au/NiCr/Ta films in crystal orientation, residual stress and resistivity was investigated. The all magnetron sputtering films were highly textured with dominant Au-(111) orientation or a mixture of Au-(111) and Au-(200) orientation. The residual stress in magnetron sputtering films at different substrate temperature was tensile stress with 155MPa-400MPa. A smallest resistivity of 3.6µΩ.cm was obtained for Au/NiCr/Ta multi-layered metallic films at substrate temperature 180°C. The experiment results reveal that the resistivity increased with the increase of the residual stress of metallic films.

Effects of Non-Continuous TiO2 Buffer Layers on Structural and Electrical Properties of Indium Tin Oxide Thin Films

Indium Tin Oxide (ITO) films on polyethylene terephthalate (PET) sandwiching TiO2 buffer layers with different sputtering time have been prepared by rf-magnetron sputtering. Scanning Electron Microscope images of the TiO2 buffer layers showed the non-continuous growth in a typical sputtered film growing process. (400) oriented diffraction peaks appeared in all the ITO/TiO2/PET films. The electrical properties were measured by four point probe method and van der Pauw method. The variations of the resistivity and hall mobility on the sputtering time of TiO2 layer were studied. Furthermore, an exponential decay correlation of resistivity and the grain size was fitted. But the linear relationship between the ITO grain size and the mobility indicated by the grain boundary scattering theory didn’t appear here. The reason is believed to neglect the influence of the local variations of the lattice spacing and some other important scattering mechanisms such as lattice, ionized impurity, neutral impurity scattering, etc.

Surface Morphology, Crystal Orientation and Scratch Properties of Au/NiCr/Ta Multi-Layered Metallic Films

The crystal orientation, surface morphology, surface roughness and scratch properties of Au/NiCr/Ta multi-layered metallic films was examined by X-ray diffraction (XRD), atomic force microscopy (AFM) and a scratch test method, respectively. It was clarified that the surface morphology and surface roughness depend on the substrate temperature. The surface roughness decreases from 4.259nm to 2.935nm when substrate temperature changed from 100°C to 180°C, and then increases when substrate temperature above 180°C. The XRD revealed that there are only Au diffraction peaks with highly textured having a Au-(111) or a mixture of Au-(111) and Au-(200) orientation. The micro-scratch test reveals that both modes can be used for conventionally critical load determination, but the friction mode can additionally reflect the changes at different metallic film layers, the critical characteristic load was not sensitive to substrate temperature.