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We demonstrated the nonvolatile memory functionality of nano-crystalline silicon (nc-Si) field effect transistors (FETs) using mobile protons that are generated by very short time (within 2 minutes) hydrogen neutral beam (H-NB) treatment at room temperature (25 °C). Some researches try to hydrogen insertion process via long time (40 minutes) high-pressure hydrogen annealing (HPHA) at high temperature (400 °C) that also need several steps such as poly silicon deposition, HPHA process, and poly silicon etching process. However our hydrogen insertion process does not need any other additional process but only H-NB process during normal thin film transistor fabrication. Also the whole memory fabrication process kept under 50 °C (except SiO2deposition process; 300 °C). These nc-Si devices exhibited reproducible hysteresis, reversible switching, and nonvolatile memory behaviors in comparison with those of the conventional FET devices. We think that the memory characteristics are attributed to the movement of protons between the Si(gate)/SiO2(gate insulator) interface and the SiO2/nc-Si thin film (active layer) interface by the applied gate electric field. Our study will further provide a useful route of creating memory functionality and incorporating proton-based storage elements onto a modified CMOS platform for FET memory devices using nanomaterials, and probability of next generation flexible memorable electronics.

The neutral beam assisted chemical vapor deposition (NBaCVD) system can control the crystalline phase and the doping efficiency simultaneously by the energy of impinge neutral particle beam. During the deposition process, energetic hydrogen (H) neutral atoms transport their energy to the surface of depositing film to enhance crystallization (crystal volume fraction (Xc) up to 85%) and dopant activation (~1X1020 #/cm3, ~30 cm2/Vs) with low H ratio at near room temperature on the substrate. The increase of H neutral beam flux induces transition of crystal orientation from [111] to [311] at constant Xc and changes the carrier transport path from “grain boundary path” to “grain-to-grain percolation path” and enhances bulk mobility of the Si thin film. The various analysis data of the thin films (XRD, Raman, temperature dependent conductivity, Hall measurement) represent the evidence of very high doping efficiency at near room temperature, obvious nano-crystalline embedded polymorphous phase, and mixed transport (band and percolation) characteristics.