Electron field emission properties of carbon nanotubes during thermal heating and laser irradiation

Sodium titanate nanotubes have been prepared and modified chemically with CdSe quantum dots (QDs) using bifunctional modifiers (HS-COOH). Their photovoltaic characteristics have also been studied. The results indicate that the surface photovoltage response of nanotubes extends to the visible light region, and the intensity of surface photovoltage is enhanced after modification with CdSe QDs. The field-induced surface photovoltage spectroscopy (FISPS) shows that sodium titanate nanotubes have different photovoltaic response before and after modification. That is, the surface photovoltaic response of pure sodium titanate nanotubes increases with the enhancement of positive applied bias and decreases with the enhancement of negative applied bias. Meanwhile, the surface photovoltaic response of CdSe modified sodium titanate nanotubes is different from that of the pure sodium titanate nanotubes. The whole spectrum increases with the enhancement of applied bias at the first stage. However, when the applied bias reaches a certain value, the surface photovoltage response keeps increasing in some spectrum regions, while decreasing in other spectrum regions. This novel phenomenon is explained by using an electric field induced dipole model. sodium titanate nanotube, CdSe, surface photovoltage spectroscopy, diffusion mechanism, drift mechanism

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The effects of laser parameters on the production of fast electrons from laser-multihole array target interaction are investigated theoretically via two-dimensional particle-in-cell simulations. The results show that the fast electron temperature is scaled by 𝐼 1/2 𝜆 2 with 𝐼 and 𝜆 being the laser intensity and wavelength. When the laser intensity reaches 2.14 × 10 20 W•cm −2 , a typical bi-Maxwellian energy distribution is observed. The slope temperature of the low-energy component fits the linear scaling 𝑇 ℎ ∼ 𝐼 1/2 well. The high-energy component has an increased slope temperature comparable to ponderomotive potential scaling law. In addition, the electron temperature rises linearly with the pulse duration, 𝑇 ℎ ∼ Δ𝑡. The divergence angle of the fast electrons increases with laser intensity and pulse duration, but is independent of laser wavelength.