54
A. Hu et al.
Fig. 1.38 a schematic of a hemi-quinone molecular structure [211]
Currently, the Hartree–Fock self-consistent field theory and the density functional
theory (DFT) are two main theories used in developing a theoretical fundamental for
molecular electronic devices.
Based on the concept of molecular electronic devices, molecular capacitors/memory units are developed as well. Jurow et al. have been reported a detailed
review of porphyrins, which elucidated a potential for using these molecules in the
fabrication of molecular capacitors [214]. Coming to molecular diodes and molecular
transistors, molecular devices functional on dielectrics material and tunable dielectric
constant are desired. In 2007, Chen et al. reported a hafnium dioxide (HfO 2 ) based
metal-insulator-molecule-metal device [215]. A HfO 2 dielectric layer was deposited
by an atomic layer deposition process. Although new studies provide an excellent
potential for deployment of the molecular capacitor, current understanding of the
molecular mechanism of the capacitor are not yet well experimentally established.
On the other hand, to establish a complete molecular electronic system, the development of molecular isolator and conductive wire is also necessary. For any integrated circuit, the isolator plays a significant role in regulating the flow of current.
Many molecular with specific functional groups can be used as molecular insulator
material. Currently, aliphatic organic molecular is considered as the best molecular
insulator [216]. In aliphatic organic molecular, there are only σ bonds existing. By
inserting these molecules between electrodes, it is very easy to break the pass current
flow. Similar to the isolator, the concept of the molecular wire is crucial when dealing
with the molecular electronics system. Different from molecular isolators, molecular
wire requires high electrical conductivity. There are two primary types of molecular
wires can be classified: saturated chains and conjugated chains [16, 217]. The main
difference between the two chains is that whether atoms are connected with single
bonds or connected by alternate single and double bonds [218]. In the development
of molecular wire, CNTs are considered as a widely acceptable material [219].
A. Hu et al.
Fig. 1.38 a schematic of a hemi-quinone molecular structure [211]
Currently, the Hartree–Fock self-consistent field theory and the density functional
theory (DFT) are two main theories used in developing a theoretical fundamental for
molecular electronic devices.
Based on the concept of molecular electronic devices, molecular capacitors/memory units are developed as well. Jurow et al. have been reported a detailed
review of porphyrins, which elucidated a potential for using these molecules in the
fabrication of molecular capacitors [214]. Coming to molecular diodes and molecular
transistors, molecular devices functional on dielectrics material and tunable dielectric
constant are desired. In 2007, Chen et al. reported a hafnium dioxide (HfO 2 ) based
metal-insulator-molecule-metal device [215]. A HfO 2 dielectric layer was deposited
by an atomic layer deposition process. Although new studies provide an excellent
potential for deployment of the molecular capacitor, current understanding of the
molecular mechanism of the capacitor are not yet well experimentally established.
On the other hand, to establish a complete molecular electronic system, the development of molecular isolator and conductive wire is also necessary. For any integrated circuit, the isolator plays a significant role in regulating the flow of current.
Many molecular with specific functional groups can be used as molecular insulator
material. Currently, aliphatic organic molecular is considered as the best molecular
insulator [216]. In aliphatic organic molecular, there are only σ bonds existing. By
inserting these molecules between electrodes, it is very easy to break the pass current
flow. Similar to the isolator, the concept of the molecular wire is crucial when dealing
with the molecular electronics system. Different from molecular isolators, molecular
wire requires high electrical conductivity. There are two primary types of molecular
wires can be classified: saturated chains and conjugated chains [16, 217]. The main
difference between the two chains is that whether atoms are connected with single
bonds or connected by alternate single and double bonds [218]. In the development
of molecular wire, CNTs are considered as a widely acceptable material [219].