Resistivity reduction of boron-doped multiwalled carbon nanotubes synthesized from a methanol solution containing boric acid

Abstract

Boron-doped multi-walled carbon nanotubes (MWNTs) were synthesized using a methanol solution of boric acid as a source material. Accurate measurements of the electrical resistivity of an individual boron-doped MWNT was performed with a four-point contact, which was fabricated using an electron beam lithography technique. The doped boron provides conduction carriers, which reduces the resistivity of the MWNT.

Electrical properties of boron-doped MWNTs synthesized by hot-filament chemical vapor deposition

“…5 shows the temperature dependence of normalized resistivity q/q RT , the electrical resistivity was normalized by the value at 300 K. The q/q RT was increased nonlinearly with decreasing temperature. The q/q RT of the MWNTs synthesized by the hot-filament CVD was over 5.0 below 50 K, while that of the MWNTs synthesized by the thermal CVD was less than 2.0 even at 2 K as reported in our previous study [5]. These results indicate that the hot-filament CVD technique generated many defects in the MWNTs because the disorders due to the structural defects lead to localization of electrons at low temperatures [12].…”

“…Meanwhile, the full-width at half maximum (FWHM) of the G bands in the nondoped and boron-doped MWNTs were 51 and 48 cm À1 , respectively. The FWHM of the G band was changed little by the borondoping and lower than that of the boron-doped MWNTs synthesized by the thermal CVD using the same source solution [4,5]. The FWHM of the G band may be attributed to the inhomogeneity of the boron concentration in the MWNTs [4,5], and therefore the hot-filament CVD technique might distribute the boron more homogeneously over the MWNTs compared to the thermal CVD.…”

“…The q/q RT was higher than that of the MWNTs synthesized by the thermal CVD and increased with decreasing temperature [5]. Because the substrate was placed near the filament, the plasma induced by the filament may have generated defects which enhance the resistivity in the grown MWNTs.…”

“…An Si substrate covered with thermally grown SiO 2 (500 nm thick) was placed within 1 mm below the filament. Before the growth, the surface of the substrate was coated with an Al layer (5 nm thick) by thermal evaporation, and then coated with an iron acetate by dipping followed by heating at 400°C for 5 min [3][4][5]9]. When the voltage was applied to the filament, the source solution in the To evaluate the electrical properties, the temperature dependence of resistivity was measured from room temperature down to 2 K. For accurate measurement, a four-terminal method was performed with metal electrodes, which were fabricated on an individual target MWNT by electron beam lithography [3].…”

Special electronic structures and quantum conduction of B/P co-doping carbon nanotubes under electric field using the first principle

“…What's more, chemical doping [6] is expected to substantially increase the density of free charge carriers and thereby to enhance the electrical and thermal conductivity. Therefore, there are a lot of works including theoretical and experimental studies for doped carbon nanotubes such as boron and nitrogen doped carbon nanotubes [7], [8], [9], [10]. However, phosphorus doped carbon nanotubes has a more complex energy band structure with the presence of two nondispersive P-related bands, one in the valence band and another in the conduction band [11].…”