In the same way that gases react with surfaces from above, solid-state point defects such as interstitial atoms can react from below. Little attention has been paid to this form of surface chemistry. Recent bulk self-diffusion measurements near the $\mathrm{Si}\left(100\right)$ surface have quantified Si interstitial annihilation rates, and shown that these rates can be described by an annihilation probability that varies by two orders of magnitude in response to saturation of surface dangling bonds by submonolayer gas adsorption. The present work shows by modeling that the interstitial annihilation kinetics are well described by a precursor mechanism in which interstitials move substantial distances parallel to the surface before incorporation.

In this study, the gamma ray radiation effect on the characteristics of inkjet-printed semiconducting single-walled carbon nanotubes (sSWCNTs) thin-film transistors (TFTs) is investigated. The devices with top gate dielectrics consisted of BaTiO₃ and poly(methyl methacrylate) (PMMA) were characterized before and after 150 krad ⁶⁰Co gamma radiation in air. It reveals that the radiation results in a positive threshold voltage shift from -0.5 to 3.6 V (with a drain voltage biased at -1 V). The hysteresis decreases slightly from 1.2 to 0.5 V, indicating that the BaTiO₃/PMMA dielectric layer effectively encapsulates the sSWCNTs TFTs from absorbing molecules in the environment. Furthermore, the charge pumping current I_CP is measured with a gate voltage pulsed at 100 kHz. The maximum I_CP increases from 90 to 140nA, which translates to an increase in the interface trap density from 4.5×10¹¹ to 1.1×10¹² cm^-2eV^-1. The charge pumping measurements at the frequency of 10∼250 kHz show that the increase of I_CP induced by radiation is obvious when f>30 kHz but is little when f<30 kHz, which indicates that the radiation induced charge traps locate near sSWCNTs. The BaTiO₃/PMMA gate dielectric remains to be a good insulator with a leakage current of less than 60 pA after radiation. Such printed flexible TFTs with the polymer gate dielectric possess similar radiation tolerant compared to convention devices on rigid substrates.

A silicon-based bilateral diode for fast neutron dose measurement is presented to take advantage of vertical and lateral current distributions and to achieve high uniform current distribution. The structure is designed to place rectangle p+ and n+ contacts on each side of the n-Si wafer. Diodes with different structure parameters are fabricated and the sensitivity to neutron dose is measured. It is found that, in this research, the increase in the lateral space between the two contacts can effectively increase sensitivity. Furthermore, the decrease of the contact length and the increase of current density can also increase sensitivity. The measured sensitivity data are verified with the model.

Metallic wafer bonding is becoming a key enabling technology in microelectromechanical systems packaging and heterogeneous integration. We realize the bonding of silicon (Si) wafers coated with aluminum (Al) film with thin tin (Sn) film as the intermediate layer. The bonding pressure is 0.25 MPa. The bonding is achieved at temperatures as low as 280°C after a short bonding time of 3 min. The average bonding strength is 9.9 MPa. The minimum variation of bonding layer thickness is about 0.2 μm within a large area. A fracture surface study and a cross-section analysis are conducted and the bond mechanism is investigated. It is found that the fracture mainly occurs at Al/Sn interface during the shear test. Two bonding conditions are compared and the results show that applying bonding pressure before heating is important to achieve a uniform bonding layer.