Single Crystalline Boron Nanocones: Electric Transport and Field Emission Properties

Wang, Xingjun; Hui, Hui; Yang, Tao; Bao, Lihong; Chen, Hui; Fei, Liu; Shen, Chengmin; Gu, Changzhi; Xu, Ning; Gao, Hongjun

doi:10.1002/adma.200701336

Cited by 84 publications

(66 citation statements)

References 39 publications

(47 reference statements)

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“…The signal of B 1s spectrum at 187.89 eV is the dominant bond, which is attributed to the B-B bond. This value of binding energy is quite reasonable considering the value of bulk boron (187.3-187.9 eV) [20][21][22]. The components at 188.46 eV in Figure 4 …”

Section: Structure and Composition Analysissupporting

confidence: 73%

Fabrication and characterization of boron nanowires at relatively low temperature

Geng

et al. 2010

Sci. China Phys. Mech. Astron.

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Large-scale crystalline boron nanowires (BNWs) were synthesized by a simple chemical vapor deposition method on Au-coated Si substrates using two kinds of innoxious and inexpensive reactant materials as the precursor at relatively low temperature (≤1000°C). The morphology and structural properties of samples were characterized by SEM, TEM, SAED, and XPS analytic instruments. The BNWs have lengths of several tens of micrometers with diameters of 80-150 nm. SAED and HRTEM analytic results testified that BNWs were single crystal core with a thin oxide sheath. By comparison of the BNW samples synthesized at difference temperatures, we conclude that BNWs have lower growth rate at 950°C, whilst the suitable growth rate can be gained at 1000°C. This result shows that BNWs can be synthesized via one step CVD process at 1000°C, and overly high growth temperature (≥1200°C) is probably unnecessary. boron nanowires, CVD method, low temperature PACS: 81.05.Bx, 81.10.BkIn recent years, one-dimensional (1D) boron nanostructure has aroused greatly interesting research from both scientific and technological areas, because it has unique chemical and physical properties and its theoretically tubular structure may have higher electrical conductivity than carbon nanotubes [1][2][3][4][5][6][7]. These properties make boron or boride nanostructures potentially use in high-temperature devices, fusion-reactor wall components, thermoelectric energy conversion, especially for the application of field emission (FE), cold-cathode materials, field effect transistors (FET), and so on [8,9]. It is interesting and important to synthesis and investigation of boron nanostructures and their properties.Many efforts focused on synthesizing amorphous and crystalline BNWs and boron nanobelts (BNBs). The synthesis methods include chemical vapor deposition (CVD) [10,11], laser ablation [12-15], vapor-transport [16,17], and magnetron sputtering [18,19], etc. Among these methods motioned above, CVD is a especially attractive method because of the compatibility of CVD with conventional semiconductor device fabrication, and it could allow controlled, selective growth of nanostructures by patterning metal catalysts on the substrates.Although the synthesis of amorphous and crystalline BNWs or BNBs with CVD method have been reported, some deficiencies still exist. For example, the reaction source (B 2 H 6 ) is poisonous, which is harmful to the researchers and environment [10]. In one-step CVD process, the reaction temperature is relatively high (≥1200°C) when the reactants are solid powders [11]. In general, a higher reaction temperature will definitely be accompanied with high deposition rate and growth rate of nanowires. It is well known that lower growth rate is helpful to improve the uni-

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Section: Structure and Composition Analysissupporting

confidence: 73%

Fabrication and characterization of boron nanowires at relatively low temperature

Geng

et al. 2010

Sci. China Phys. Mech. Astron.

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“…So far, to our knowledge, while both amorphous [15][16][17][18][19][20] and crystalline boron nanowires [21,22] have been fabricated by magnetron sputtering, laser ablation, or chemical vapor methods, vertical arrays of single-crystal boron nanowires over a large area have not been synthesized in a one-step process. In addition, little attention [23][24][25] has been paid to the measurements of the physical properties of an individual boron nanowire. In this Communication, we report the successful synthesis of high-density, vertically aligned single-crystal boron nanowire arrays with a nanowire diameter of approximately 20-40 nm by a thermal carbon-reduction method.…”

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“…This 22% instability at high current is acceptable for the following reasons: 1) Part of the fluctuation comes from vacuum pump vibrations, which give rise to a slight change of the distance between the probe and the sample during the FE measurements; 2) At more commonly used lower working currents, the stability should be considerably improved, as reported in our recent work. [23,32] Our recent results show that an individual boron nanowire has a higher conductivity of 1.…”

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confidence: 99%

Fabrication of Vertically Aligned Single‐Crystalline Boron Nanowire Arrays and Investigation of Their Field‐Emission Behavior

et al. 2008

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Elemental boron arouses great interest from both scientific and technological areas of research because it has unique chemical and physical properties and its theoretical tubular structures may have higher electrical conductivity than carbon nanotubes. [1][2][3][4][5][6][7] High conductivity and chemical stability of boron or boride nanostructures have made it an attractive candidate for future applications in ideal cold-cathode materials, high-temperature semiconductor devices, or fieldeffect transistors. [8][9][10][11][12][13][14] In particular, for the application of field emission (FE), it is especially useful to synthesize large, vertical arrays of boron nanowires (BNWs) with the desired surface work function and FE behavior. So far, to our knowledge, while both amorphous [15][16][17][18][19][20] and crystalline boron nanowires [21,22] have been fabricated by magnetron sputtering, laser ablation, or chemical vapor methods, vertical arrays of single-crystal boron nanowires over a large area have not been synthesized in a one-step process. In addition, little attention [23][24][25] has been paid to the measurements of the physical properties of an individual boron nanowire. In this Communication, we report the successful synthesis of high-density, vertically aligned single-crystal boron nanowire arrays with a nanowire diameter of approximately 20-40 nm by a thermal carbon-reduction method. Moreover, we have measured the FE behavior and surface work function of a single boron nanowire, which is critical to evaluate the possibility of using boron nanowires as field-emission materials. For the purpose of better understanding the field-emission mechanism of a boron nanowire, the field-emission properties of a BNW film are also measured to compare with those of an individual nanowire. Figure 1 shows large-scale boron nanowire arrays on a Si(001) substrate after approximately 2-4 h of growth. As shown in Figure 1A, the high-density arrays are aligned vertically on the silicon substrate. Figure 1B is the highresolution scanning electron microscopy (SEM) image of the aligned BNWs, in which one can see that the length of the BNW is about 5 mm and the morphology of the nanowires is uniform. The aspect ratio of each boron nanowire is about 200, which is high enough for a field-emission application. The side and top views of the boron nanowire are shown in Figure 1C and D, respectively, which reveals the detailed morphology of the BNWs. The boron nanowires have a diameter of about 20-40 nm and no catalyst is found at their tip. The catalysts, however, were found to lie on the substrate arbitrarily when we peeled off some nanowire film from the substrate, as shown in Figure 1C. Thus, we believe that the growth is through a vapor-liquid-solid (VLS) mechanism and the binding force between the Fe 3 O 4 catalyst and the silicon substrate is strong. This strong binding leads to good conductivity between the boron nanowires and the substrate, which may contribute to their good field-emission properties. The alignment of BNWs can...

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“…Superconducting properties are also altered when the effective size of a superconductor is reduced [7][8][9][10][11][12][13][14][15][16]. Progress in preparation of boron nanomaterials [18][19] motivated this investigation of solid-solid phase transition and physical properties at ambient and at high pressures. In this study, we report observations of semiconductor-metal-superconductor transitions in crystalline boron nanowires (BNWs) under high pressure.…”

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confidence: 99%

“…All forms mentioned above have the common structural component of boron icosahedrons B 12 in the unit cell [21]. To determine the structural properties, the BNW samples fabricated by chemical vapor deposition [19] were characterized using scanning electron microscopy (SEM), 3 transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and X-ray diffraction (XRD) measurement. High-pressure experiments were performed using a diamond anvil cell made of BeCu alloy.…”

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confidence: 99%

Pressure-induced superconducting state in crystalline boron nanowires

et al. 2009

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We report high-pressure induced superconductivity in boron nanowires (BNWs) with rhombohedral crystal structure. Obviously different from bulk rhombohedral boron, , , these BNWs show a semiconductor-metal transition at much lower pressure than bulk boron. Also, we found these BNWs become superconductors s s with Tc= = = 1.5 K at 84 GPa, at the pressure of which bulk boron is still a semiconductor, via in-situ resistance measurements in a diamond anvil cell. With increasing pressure, Tc of the BNWs increases. The occurrence of superconductivity in the BNWs at a pressure as low as 84GPa probably arises from the size effect. 2 It is well-known that bulk solid boron is a semiconductor with a band gap of~2 eV at ambient pressure. Theoretical calculations predicted that at sufficient high pressure, band overlap occurs, which drives s s the bulk boron to a poor metal [1][2]. Recently, , , two striking resistance measurements under high pressure found that the semiconductor-metal transition occurs at room temperature in bulk -boron at 130 GPa [3] and in bulk -boron at 160 GPa [4]. At low temperature, they both showed a superconducting transition at~4 K and 160 GPa. Nanomaterials with the same crystal structure as the corresponding bulk solid are expected to have interesting physical properties in comparison with their bulk counterparts. For example, when the size of the solid is small enough, solid-solid phase transition pressures s s vary with size change [5][6]. Superconducting properties are also altered when the effective size of a superconductor is reduced [7][8][9][10][11][12][13][14][15][16]. Progress in preparation of boron nanomaterials [18][19] motivated this investigation of solid-solid phase transition and physical properties at ambient and at high pressures. In this study, we report observations of semiconductor-metal-superconductor transitions in crystalline boron nanowires (BNWs) under high pressure. In addition, the pressure dependence of the superconducting critical temperature (Tc) was studied up to 240 GPa. The correlation between the measured value of Tc and pressure in BNWs is compared with the data of bulk solid boron. High-pressure experiments were performed using a diamond anvil cell made of BeCu alloy. Diamonds were selected carefully for very low birefringence with tips whose diameter is 300 m for the first experiment and 40 m for the second. A standard fourlead technique was used for the first experiment below 60 GPa and a pseudo four-lead technique was used for the second experiment. The pseudo four-lead pattern was made by thin-film fabrication and photolithography technology. A layer of titanium (Ti) was 4 deposited onto the diamond surface, followed by a layer of platinum deposited over the Ti layer. Four layered leads were then connected to 5µm-thick Pt wires. Insulation from the rhenium gasket was achieved by a thin layer of a mixture of diamond powder and epoxy. The size of each wire sample used in this study was measured under a high magnification observation microscope. Seven ...

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Single Crystalline Boron Nanocones: Electric Transport and Field Emission Properties

Cited by 84 publications

References 39 publications

Fabrication and characterization of boron nanowires at relatively low temperature

Fabrication and characterization of boron nanowires at relatively low temperature

Fabrication of Vertically Aligned Single‐Crystalline Boron Nanowire Arrays and Investigation of Their Field‐Emission Behavior

Pressure-induced superconducting state in crystalline boron nanowires

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