Constructing globally distributed file systems (DFS) has received great attention. Traditional Peer-to-Peer (P2P) distributed file systems have inevitable drawbacks such as instability, lacking auditing and incentive mechanisms. Thus, Inter-Planetary File System (IPFS) and Swarm, as the representative DFSs which integrate with blockchain technologies, are proposed and becoming a new generation of distributed file systems. Although the blockchain-based DFSs successfully provide adequate incentives and security guarantees by exploiting the advantages of blockchain, a series of challenges, such as scalability and privacy issues, are also constraining the development of the new generation of DFSs. Mainly focusing on IPFS and Swarm, this paper conducts an overview of the rationale, layered structure and cutting-edge studies of the blockchain-based DFSs. Furthermore, we also identify their challenges, open issues and future directions. We anticipate that this survey can shed new light on the subsequent studies related to blockchain-based distributed file systems. INDEX TERMS Blockchain, distributed file systems, IPFS, swarm.

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In this work, we report on the impact of position, bias, and workfunction of back gate on retention time of Tunnel Field Effect Transistor (TFET) based dynamic memory in ultra thin buried oxide and Double Gate (DG) transistors. The front gate of the TFET is aligned at a partial portion of the semiconductor film and controls the read mechanism based on band-to-band tunneling. The back gate is engineered to improve the performance of the dynamic cell by positioning it at the region uncovered by the front gate where it forms a deep potential well. The physical well formed by the back gate misalignment is made more profound by using a p+ poly workfunction as it accumulates more holes in the storage region and forms a deep potential well that sustains holes for longer duration, thereby increasing the retention time. The retention time is also governed by the generation and recombination phenomenon which can be controlled through the applied bias at the back gate. The retention time attained is ∼2 s at a temperature of 85 °C through optimal back gate engineering in DG transistors. The work shows innovative viewpoints of transforming gate misalignment, traditionally considered detrimental into a unique opportunity, coupled with appropriate selection of back gate workfunction and bias to significantly improve the retention time of capacitorless dynamic memory.

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