Synthesis, Characterization, and Applications of Si, GaN, and InN Nanowires

Abstract

Er-doped Si NWs have been grown via a vapor transport and condensation method with ErCl3。6H2O powder as a source. The Er-doped Si NWs exhibit the room temperature PL at the wavelength of 1.54 μm, ideal for optical communication. From I-V measurements, the resistivity of 4.2 at. % Er-doped Si NWs was determined to be 1.5×10-2 Ω-cm. The Er-doped Si NWs were found to possess excellent field emission properties with a field enhancement factor as high as 1260. The rich variety of physical properties exhibited by the Er-doped Si NWs points to versatile applications for advanced devices. Room temperature ferromagnetism with 1.54 μm light-emitting properties has been discovered for Er-doped Si nanocables. The Er-doped Si nanocables were synthesized via the vapor transport and condensation method using the ErCl3．6H2O as the doping source. The doping concentration of Er within the Si nanocables could be controlled via varying the weight ratio of Si:ErCl3．6H2O. The saturation magnetism was found to increase with the Er concentration and decrease in temperature. The novel optical and magnetic properties indicate that Er-doped Si nanocables have the potential for applications of nanoscale Si-based spintronics or optoelectronics. Three-fold symmetrically distributed GaN NW arrays have been epitaxially grown on GaN/sapphire substrates. The GaN NW possesses a triangular cross section enclosed by (000 ), (2 2), and ( 112) planes and the angle between the GaN NW and the substrate surface is about 62°. The GaN NW arrays produce negative output voltage pulses when scanned by a conductive AFM in contact mode. The average of piezoelectric output voltage was about -20 mV, while 5%-10% of the NWs had piezoelectric output voltages exceeding –(0.15-0.35) V. The GaN NW arrays are highly stable and highly tolerate to moisture in the atmosphere. The GaN NW arrays demonstrate an outstanding potential to be utilized for piezoelectric energy generation with a performance probably better than ZnO NWs. InN NWs have been successfully synthesized via the thermal evaporation and condensation process. The synthesis of InN NWs is based on the VLS process and the growth direction of InN NWs is along [01 0]. Based on the calculated results, the magnitude and distribution of the piezopotential in a bent InN NW are found to strongly depend on the growth direction of the NW. If the diameter, length, and applied force are the same, the magnitude of the negative as well as positive piezopotential in the InN NW with a [01 0] growth direction would be almost 20 times larger than that in the InN NW with a [0001] growth direction. The piezopotential of a bent InN NW growing along [01 0] can be positive, negative and zero depending on the direction of the applied transverse force. By measuring the output voltage of a InN NW based nanogenerator, about 40% to 55% of output voltages are within the ranges from -1 to -20 mV and 25% to 30% of output voltages would exceed -100 mV. Some output voltages could reach the magnitude of -1000 mV, showing its great potential for fabricating high output nanogenerators.