The well-known Bogoliubov expression for the spectrum of a weakly interacting dilute Bose gas becomes inadequate when the density or interactions strength is increased. The corrections to the spectrum due to stronger interactions were first considered by Beliaev (1958 Sov. Phys.-JETP 7 289). We revisit Beliaev's theory and consider its application to a dilute gas with van der Waals interactions, where the scattering length may be tuned via a Fano-Feshbach resonance. We numerically evaluate Beliaev's expression for the excitation spectrum in the intermediate-momentum regime, and we also examine the consequences of the momentum dependence of the two-body scattering amplitude. These results are relevant to the interpretation of a recent Bragg spectroscopy experiment of a strongly interacting Bose gas.
We demonstrate for the first time the crystallization of amorphous Si induced by Ni colloid printing using inkjet printing technology. An electrostatic inkjet nozzle having a needle inside a capillary was built in house, which was able to eject very fine droplets according to the applied electric voltage. Dots of Ni colloidal solution were formed in the prescribed position. Enhanced crystallization was observed at the Ni-colloid-printed sites. The probability of crystallization decreased with the Ni concentration in the solution. At and above 4 mass % Ni concentration, fully enhanced crystallization occurred. Furthermore, the orientation of crystallized Si grains was determined by electron-backscattering pattern (EBSP) analysis. The dependence of crystallization behavior on the Ni concentration was also investigated.
We demonstrated for the first time single-crystal grain growth in the solid-phase crystallization of amorphous silicon (a-Si) film induced by inkjet-printed colloidal solution containing Ni nanosized particles. The electrostatic inkjet nozzle with a needle can print dots of Ni colloidal solution, whose size ranges from submicron order to a few ten micrometers, on the a-Si film surface by controlling the needle apex radius and the number of applied voltage pulses. The dependence of the crystallization behavior of a-Si on dot size is investigated by electron backscattering pattern (EBSP) analysis. Crystallization behavior is categorized into three modes: single-crystal growth, polycrystal growth, and lateral-crystal growth. Statistical analysis suggests that, when the dot size is 0.86 µm in diameter, a single-crystal grain is grown at the inkjet-printed sites with a probability of 0.62.
Performance of thin film transistor (TFT) whose channel is fabricated by using a solution process of single-walled carbon nanotube (SWCNT) has been studied. SWCNT solution is prepared by using 9,9-dioctyfluorenyl-2,7-diyl–bipyridine (PFO–BPy) copolymer as solubilizer. Over 4 decades' on/off ratio is obtained by using drop-coating at room temperature without any further optimization. Other solubilizers are chosen as control groups to measure the on/off ratio of SWCNT TFT to investigate effects of the use of PFO–BPy. Results suggest that thick SWCNT network should be uniformly established at the channel region and the channel is required to be formed with well-separated SWCNTs.
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