Metal-insulator-metal diodes based on alkyltrichlorosilane self-assembled monolayers (original) (raw)
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RSC Adv., 2014
A study of the self-assembly of silver atom intercalated 5,5 0 -bis(mercaptomethyl)-2,2 0 -bipyridine (BPD; HS-CH 2 -(C 5 H 3 N) 2 -CH 2 -SH) and 1,4-benzenedimethanethiol (BDMT; HS-CH 2 -(C 6 H 4 )-CH 2 -SH)) dithiol (DT) multilayers on gold is presented. The bilayer of these SAMs can be obtained starting from the exposure of a DT monolayer to a concentrated silver ion solution. After grafting the silver atoms on the sulfur end group, the incubation of the resulting DT-Ag SAM in a DT solution leads to the formation of a DT-Ag-DT bilayer. This process was extended to make a multilayer structure. The corresponding changes in these self-assembled layers on Au are characterized by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) measurements, and I-V characteristics. Our interpretation of evolution in the absorbed layer are based on changes in intensities of peaks in XPS related to S bound to substrate or Ag and in -SH groups, as well as changes in thickness and absorption features in SE measurements. The latter show the evolution in absorbance wavelength as a function of thickness and indicate a decrease in the HOMO-LUMO gap from about 4.5 eV to 4 eV. The I-V characteristics show a significant bias dependence on the number of the BPD layers and there appears to be a transition from tunneling to a hopping regime when going from the single to the multiple layers.
Electrical properties of end-group functionalised Self-Assembled Monolayers
Microelectronic Engineering, 1997
In a previous study we have demonstrated that a single monolayer of alkyl-trichlorosilane molecules, covalently bonded to the native oxide of a silicon substrate, allows the fabrication of MIS (Metal-Insulator-Semiconductor) devices with excellent electrical properties [C.Boulas et AI., Phys. Rev. Lett. 76, 4797(1996)]. Here we demonstrate that we can ftmctionalise the end-groups of the molecules, once grafted to the substrate, without disturbing the excellent insulating properties of the monolayer. The functionalisation of the monolayer is monitored by FTIR and ellipsometry. Conductivity, photoconductivity and capacitance measurements are performed to study the effect of the chemical functionalisation on the electrical properties of the monolayer. Finally, possible sub-0.1 ttm device applications are presented.
Modification of metal/semiconductor junctions by self-assembled monolayer organic films
Microelectronic Engineering, 2009
Two new metal/molecule/semiconductor contacts, Au/n-Si/TDA/Au and Au/p-Si/ODM/Au, were fabricated to understand effect of organic compounds, tridecylamine and octadecylmercaptan self-assembled monolayer (SAM) films, on electrical charge transport properties of the metal/semiconductor junctions. The morphology of the organic monolayers deposited on Si substrates was investigated by atomic force microscopy. The molecular coverage of ODM deposited on p-Si is poorer than that of TDA on n-Si substrate. The ideality factors of the p-Si/ODM and n-Si/TDA diodes were found to be 1.66 and 1.48, respectively. The electrical results show that the tridecylamine monolayer passivated junction has a lower ideality factor. The ideality factor indicates clear dependence on two different type functional groups R-SH (Thiol) and R-NH 2 (Amin) groups and it increases with different functional groups of organic molecule. The barrier height u b value of the n-Si/TDA diode is smaller than that of p-Si/ODM diode, as a result of chain length of the SAM organic molecules. The interface state density D it values of the diodes were determined using conductance technique. The n-Si/TDA diode has the smaller interface state density according to p-Si/ODM diode. We have evaluated that the organic molecules control the electronic parameters of metal/semiconductor diodes and thus, organic modification helps to get one step closer towards to new organic assisted silicon based microelectronic devices.
Self-assembled monolayer effect on the characteristics of organic diodes
Synthetic Metals, 2009
In this paper, we study the effect of self-assembled monolayers (SAMs) on the electric behavior of organic diodes based on sexithiophene (6T) sandwiched between indium tin oxide (ITO) and aluminum. We have used molecules of SAMs based on a thiol with functional groups of oligothiophene (3T(CH 2 ) 6 SH). Wettability measurements have been performed to characterize ITO surface energy and its modification upon deposition of SAMs. The results of contact angle measurements and surface energies demonstrate the homogeneity and rigidity of grafting surface. The current vs. applied voltage characteristics of devices show that conduction in weak biasing follow Richardson-Schottky behavior. Beyond 1.5 V, J-V characteristics can be successfully modeled by space-charge limited current (SCLC) theory followed by a trap charge limited current (TCLC). The electrical as well as optical characteristics of 6T layer are clearly affected by the presence of the SAM. The differences between ITO/SAM and bare ITO samples are interpreted in terms of structural effect induced by the self-assembled monolayer of 3T(CH 2 ) 6 SH.
Solid-State Electronics, 2012
The femtosecond-fast transport in metal-insulator-metal (MIM) tunnel diodes makes them attractive for applications such as ultra-high frequency rectenna detectors and solar cells, and mixers. These applications impose severe requirements on the diode current-voltage I(V) characteristics. For example, rectennas operating at terahertz or higher frequencies require diodes to have low resistance and adequate nonlinearity. To analyze and design MIM diodes with the desired characteristics, we developed a simulator based on the transfer-matrix method, and verified its accuracy by comparing simulated I(V) characteristics with those measured in MIM diodes that we fabricated by sputtering, and also with simulations based on the quantum transmitting boundary method. Single-insulator lowresistance diodes are not sufficiently nonlinear for efficient rectennas. Multi-insulator diodes can be engineered to provide both low resistance and substantial nonlinearity. The improved performance of multi-insulator diodes can result from either resonant tunneling or a step change in tunneling distance with voltage, either of which can be made to dominate by the appropriate choice of insulators and barrier thicknesses. The stability of the interfaces in the MIIM diodes is confirmed through a thermodynamic analysis.