Role of ALD Al2O3 Surface Passivation on the Performance of p-Type Cu2O Thin Film Transistors

High-performance p- type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switching characteristics were improved by applying a thin ALD Al2O3 passivation layer on the Cu2O channel, followed by vacuum annealing at 300 degrees C. Detailed characterization by transmission electron microscopy-energy dispersive X-ray analysis and X-ray photoelectron spectroscopy shows that the surface of Cu2O is reduced following Al2O3 deposition and indicates the formation of a 1-2 nm thick CuAlO2 interfacial layer. This, together with field-effect passivation caused by the high negative fixed charge of the ALD Al2O3, leads to an improvement in the TFT performance by reducing the density of deep trap states as well as by reducing the accumulation of electrons in the semiconducting layer in the device off-state.Peer reviewe

Reduced boron diffusion under interstitial injection in fluorine implanted silicon

Point defect injection studies are performed to investigate how fluorine implantation influences the diffusion of boron marker layers in both the vacancy-rich and interstitial-rich regions of the fluorine damage profile. A 185 keV, 2.3?1015 cm?2 F+ implant is made into silicon samples containing multiple boron marker layers and rapid thermal annealing is performed at 1000 °C for times of 15–120 s. The boron and fluorine profiles are characterized by secondary ion mass spectroscopy and the defect structures by transmission electron microscopy ?TEM?. Fluorine implanted samples surprisingly show less boron diffusion under interstitial injection than those under inert anneal. This effect is particularly noticeable for boron marker layers located in the interstitial-rich region of the fluorine damage profile and for short anneal times (15 s). TEM images show a band of dislocation loops around the range of the fluorine implant and the density of dislocation loops is lower under interstitial injection than under inert anneal. It is proposed that interstitial injection accelerates the evolution of interstitial defects into dislocation loops, thereby giving transient enhanced boron diffusion over a shorter period of time. The effect of the fluorine implant on boron diffusion is found to be the opposite for boron marker layers in the interstitial-rich and vacancy-rich regions of the fluorine damage profile. For marker layers in the interstitial-rich region of the fluorine damage profile, the boron diffusion coefficient decreases with anneal time, as is typically seen for transient enhanced diffusion. The boron diffusion under interstitial injection is enhanced by the fluorine implant at short anneal times but suppressed at longer anneal times. It is proposed that this behavior is due to trapping of interstitials at the dislocation loops introduced by the fluorine implant. For boron marker layers in the vacancy-rich region of the fluorine damage profile, suppression of boron diffusion is seen for short anneals and then increased diffusion after a critical time, which is longer for inert anneal than interstitial injection. This behavior is explained by the annealing of vacancy-fluorine clusters, which anneal quicker under interstitial injection because the injected interstitials annihilate vacancies in the clusters

Design and Simulation of a Mechanical Amplifier for Inertial Sensing Applications.

peer reviewe

Dental implantlar ve kullanım alanları

In this paper, a point defect injection study is performed to investigate the effect of fluorine on boron diffusion when interstitials are injected from the surface. 185keV, 2.3x1015 cm-2 fluorine is implanted into silicon with a boron marker layer located at about Rp/2 of the fluorine implant. This is followed by rapid thermal annealing at 1000oC for times 15 ~120s in an oxygen ambient. The wafers are covered with different layers prior to anneal to introduce different point defect injection effects. When interstitials are injected from the surface, fluorine strongly suppresses boron diffusion for anneal times of 15 and 30s. For longer anneal times, fluorine becomes progressively less effective and the boron diffusion coefficient approaches the value obtained in samples without fluorine. This effect of fluorine on boron diffusion suppression correlates with the presence of a shallow SIMS fluorine peak at ~Rp/2. These results support earlier work showing that vacancy-fluorine clusters at ~Rp/2 are responsible for the suppression of boron diffusion and that these clusters anneal out during long anneal times. Under inert anneal, fluorine has little effect on boron diffusion. An issue of boron cross contamination during the fluorine implant is also identified