Gettering Effects of Silicon Nitride Films from Various Plasma-Enhanced Chemical Vapor Deposition Conditions

This paper investigates and compares the impurity gettering effects of silicon nitride (SiNx) films that are synthesized by plasma-enhanced chemical vapor deposition (PECVD) under various conditions. Both industrial- and laboratory-scale PECVD systems are employed to deposit SiNx films with a wide range of properties (with refractive indices from 1.93 to 2.45 at 632 nm), which covers the entire range of SiNx used for silicon solar cells. The gettering effects are quantified by monitoring the reduction kinetics of the interstitial iron concentration in the silicon wafer bulk as iron becomes gettered to the surface SiNx layers during cumulative annealing at 400 °C. The results show that the very different SiNx films generate similar gettering kinetics, indicating that the impurity gettering effect is likely present in most PECVD SiNx films for silicon solar cells. The gettering kinetics and the SiNx film properties of refractive index, Si-N, Si-H, N-H bond densities, and H content, are found to have no clear correlations.The work of A. Liu and Y. Wan was supported by the ARENA ACAP postdoctoral fellowship scheme. The work of Z. Hameiri was supported by the Australian Research Council through the Discovery Early Career Researcher Award under Project DE150100268

High-Speed Extraction of Regions of Interest in Optical Camera Communication Enabled by Grid Virtual Division

Optical camera communication (OCC), enabled by light-emitting diodes (LEDs) and embedded cameras on smartphones, has drawn considerable attention thanks to the pervasive adoption of LED lighting and mobile devices. However, most existing studies do not consider the performance bottleneck of Region of Interest (RoI) extraction during decoding, making it challenging to improve communication capacity further. To this end, we propose a fast grid virtual division scheme based on pixel grayscale values, which extracts RoI quickly without sacrificing computational complexity, thereby reducing the decoding delay and improving the communication capacity of OCC. Essentially, the proposed scheme uses a grid division strategy to divide the received image into blocks and randomly sample several pixels within different blocks to quickly locate the RoI with high grayscale values in the original image. By implementing the lightweight RoI extraction algorithm, we experimentally verify its effectiveness in reducing decoding latency, demonstrating its superior performance in terms of communication capacity. The experimental results clearly show that the decoding delay of the proposed scheme is 70% lower than that provided by the Gaussian blur scheme for the iPhone receiver at a transmission frequency of 5 kHz

High-Accuracy Height-Independent 3D VLP Based on Received Signal Strength Ratio

Visible light positioning (VLP) has attracted intensive attention from both academic and industrial communities thanks to its high accuracy, immunity to electromagnetic interference, and low deployment cost. In general, the receiver in a VLP system determines its own position by exploring the received signal strength (RSS) from the transmitter according to a pre-built RSS attenuation model. In such model-based methods, the LED’s emission power and the receiver’s height are usually required known and constant parameters to obtain reasonable positioning accuracy. However, the LED’s emission power is normally time-varying due to the fact that the LED’s optical output power is prone to changing with the LED’s temperature, and the receiver’s height is random in a realistic application scenario. To this end, we propose a height-independent three-dimensional (3D) VLP scheme based on the RSS ratio (RSSR), rather than only using RSS. Unlike existing RSS-based VLP methods, our method is able to independently find the horizontal coordinate, i.e., two-dimensional (2D) position, without a priori height information of the receiver, and also avoids the negative effect caused by fluctuation of the LED’s emission power. Moreover, we can further infer the height of the receiver to achieve three-dimensional (3D) positioning by iterating the 2D results back into positioning equations. To quickly verify the proposed scheme, we conduct theoretical analysis with mathematical proof and experimental results with real data, which confirm that the proposed scheme can achieve high position accuracy without known information of the receiver’s height and LED’s emission power. We also implement a VLP prototype with five LED transmitters, and experimental results show that the proposed scheme can achieve very low average errors of 2.73 cm in 2D and 7.20 cm in 3D

Constraints and Recent Solutions of Optical Camera Communication for Practical Applications

Visible light communication (VLC) has emerged as a promising technology for wireless communication due to its advantages of the vast optical spectrum, high energy efficiency, and no electromagnetic interference radiation. With the widespread adoption of LED infrastructure and camera-equipped smart devices, optical camera communication (OCC) has gained momentum as a pragmatic version of VLC based on commercial off-the-shelf (COTS) devices. Compared with VLC systems based on photodiodes (PD), the information-carrying capability of OCC enables it to provide a wide range of services in the areas of intelligent transportation, indoor positioning, underwater communication, and the Internet of Things (IoT). This paper presents a brief overview of the OCC system, focuses on the constraints affecting OCC performance, and offers feasible solutions for dependable data transmission in complex and diverse scenarios. Finally, this paper summarizes the potential extended applications of OCC, hoping to push this advanced form of optical wireless communication toward practical deployments in our daily lives