Nitrogen ion beam thinning of a-SiCN diaphragm for environmental cell prepared by low-energy ion beam enhanced chemical vapor deposition

An amorphous silicon carbonitride (a-SiCN) diaphragm for environmental cell transmission electron microscopy (E-TEM) was fabricated by ion-beam-induced chemical vapor deposition (LEIBICVD) with Ar+ ions accelerated by 1.5 kV and hexamethyldisilazane (HMDSN). The diaphragms were applied to a KBr substrate or a Cu grid with 100-mu m-diameter holes. Then, the deposited film was irradiated by N+ ions accelerated at 1.5 kV for thinning and nitriding. Optical microscopy revealed that the diaphragm deflection decreased with increasing N+ ion dose. These films, which were observed by E-TEM, were amorphous and transparent to an electron beam accelerated to 300 kV and caused no charging. Fourier transform infrared spectra and X-ray photoelectron spectra revealed that higher N+ ion doses helped to eliminate organic compounds and hydrogen, and promoted the formation of Si-N and C-N bonds in diaphragms. A diaphragm with a 15 nm film thickness after etching by N+ ion irradiation was successfully developed that could resist a differential pressure of 0.3 MPa.