Field emission characteristics of metal nanoparticle-coated carbon nanowalls

Metal nanoparticles are deposited on nitrogen-incorporated carbon nanowalls (CNWs) using Ag, Au, In, and Mg as metal species for enhancing field emission. Morphology, coverage, chemical composition, and crystallinity of the metal coatings on CNW surfaces are examined by varying nominal thickness of metals within 10 nm. The emission characteristics reveal that coating CNWs with any metal species lowers emission turn-on fields and thus increases emission efficiency. The inverse dependence of field enhancement factor and turn-on field upon nominal thickness of metals confirms that additional field amplification at metal nanoparticles governs emission efficiency regardless of work functions of the metals. The Ag-coated CNWs retain the highest current density for long-time emission at a constant applied field, while the non-coated CNWs have higher emission stability and a larger time constant of current degradation than the metal-coated ones.

Controlling the Electronic Properties of a Nanoporous Carbon Surface by Modifying the Pores with Alkali Metal Atoms

We investigate a process of controlling the electronic properties of a surface of nanoporous carbon glass-like thin films when the surface pores are filled with potassium atoms. The presence of impurities on the surface in the form of chemically adsorbed hydrogen and oxygen atoms, and also in the form of hydroxyl (OH) groups, is taken into account. It is found that even in the presence of impurities, the work function of a carbon nanoporous glass-like film can be reduced by several tenths of an electron volt when the nanopores are filled with potassium atoms. At the same time, almost all potassium atoms are ionized, losing one electron, which passes to the carbon framework of the film. This is due to the nanosizes of the pores in which the electron clouds of the potassium atom interact maximally with the electrons of the carbon framework. As a result, this leads to an improvement in the electrical conductivity and an increase in the electron density at the Fermi level. Thus, we conclude that an increase in the number of nanosized pores on the film surface makes it possible to effectively modify it, providing an effective control of the electronic structure and emission properties.

Controlling the electronic properties of 2D/3D pillared graphene and glass-like carbon via metal atom doping

We present the results of investigation of the nanopore filling of planar layered and bulk pillared graphene (PGR) as well as films and 3D samples of glass-like porous carbon (GLC) with potassium atoms. The patterns of charge transfer, electronic structure, and shift of the Fermi level during the filling of nanopores with potassium atoms are established. It is found that the greatest charge transfer from potassium atoms to the carbon framework is observed in PGR with a density of 1.1-1.4 g cm^-3 (that is, with a nanopore volume of 1300-1800 nm³) regardless of the framework topology. The maximum charge transfer occurs already when the mass fraction of potassium is 12 wt%. At the same potassium concentration, a maximum shift of the Fermi level to zero by ∼3 eV occurs in a bilayer PGR film with a density of 1.4 g cm^-3. Thus, our work shows for the first time that the electronic properties of nanoporous materials doped with alkaline earth metals (in particular, potassium) can be controlled by varying the volume of doped nanopores, i.e. by controlling the density of the nanoporous material. We first demonstrated that the potassium doping of PGR would be more effective than potassium doping of GLC. It is established that 2D samples of PGR and GLC completely reproduce the electronic properties of the bulk samples and even surpass them in some parameters. To carry out research, we developed a new method for nanopore filling with dopant atoms based on both the randomness of the nanopore filling and the energy advantage of this process. This method allows us to reliably determine the maximum possible mass fraction (wt%) of dopant atoms of any porous material.

A Cu-atom-chain current channel with a width of approximately 0.246 nm on (5, 0) single-wall carbon nanotube

Continuous miniaturization with improved performance has enabled the development of electronic devices. However, further shrinking of electronic circuits will push feature sizes (linewidths) firmly into the nanoscale. This can cause electronic devices built using current materials (silicon-based) and fabrication processes to not work as expected. Therefore, new materials or preparation technologies are needed for the further miniaturization of electron devices. Here, through theoretical simulation, we show that regular doping of a Cu-atom chain on a single-wall carbon nanotube (SWCNT) can be used to realize an atomic-scale current channel (Cu-atom-chain current channel) with a linewidth of approximately 0.246 nm. Moreover, the atomic-scale Cu-atom-chain current channel shows enhanced conductivity (lower power consumption) compared to a pristine SWCNT. Such a Cu-atom-chain current channel with an atomic-scale linewidth and its method of fabrication (regular doping) may be suitable for the preparation of nanoelectronic devices.