| The excessive use of traditional fossil fuels has caused to the serious air contamination problems all over the world, affecting billions of person. Among all the noxious pollutants in air, fine particles with an aerodynamic diameter of 2.5 micrometers or less(PM2.5) are the most harmful for human health because they are small enough to invade even the smallest airways and penetrate to the lungs. Since the whole world are all suffering from a serious air pollution problem, finding renewable clean fuels and other devices are very urgent. Here I will present our recent efforts on the pursuit of new generation solar cells and memories, the water splitting solar cells and resistive random access memories（RRAM） by using thin films coated efficient samples. In our work:1) we started from the morphology, nanomechanical properties and chemical composition study on the PM2.5 particles collected in the air pollution. We combined the nanosacle mechanical and chemical properties of the PM2.5 articles for the first time. Through characterization of more than 500 particles, our study reveals that the fluffy soot particles which is rich in carbon are fluffy, rougher, unstable. They can be deformed, and they are stickier. Moreover, these soot particles can aggregate all other particles, compiling all the possible chemicals and incrementing their size, leading to higher toxicity and a risk for lungs.2) After the study on the PM2.5 nanoparticles, we think transferring the sunlight to the storable and transportable hydrogen by water splitting solar cells is very urgent for the society. In our work, we focused on the photoanodes of the water splitting cells, where oxygen evolution reaction happens. The ultra-thin（≤ 15 nm） film of Cu0 was sputtered on commercially available n-type Si wafers, resulting in Cu/SiO2/nSi photoanode. After the fabrication, the sample was experienced by a photoelectrochemical treatment in basic pH conditions, resulting in CuO/Cu/SiO2/nSi photoanode. The resulting CuO/Cu layer acts as: i) protective layer to avoid the corrosion of nSi, ii) p-type hole conducting layer for efficient charge separation and transportation, and iii) electrocatalyst to reduce the overpotential of the water oxidation reaction. The low cost, low toxicity, and good performance of CuO-based coatings can be an attractive solution to functionalize unstable materials for solar energy conversion.3) Resistive switching（RS） is the local phenomenon in the thin insulator films of RRAM, which takes place at the areas of 100 nm2, so the use of characterization tools with high lateral spatial resolution is very necessary. In our work, we investigate the origin of the resistive switching（RS） in the ultra-thin hafnium dioxide through the enhanced conductive atomic force microscope（CAFM）, which connects the standard CAFM with the semiconductor parameter analyzer working in the controlled environments. The characterization results indicate that the RS in RRAM is induced by a conductive filament（CF） formed at a grain boundary（GB） in polycrystalline stacks. And for the first time, we link the mechanical and electrical properties of the thin insulator film to study the CF-based RS. Our study reveals that reversible CFs preferably form and propagate only at GBs, which are mechanically weak spots. |
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