Eun-Kyoung Jeon

Aptamers as molecular recognition elements for electrical nanobiosensors

AbstractRecent advances in nanotechnology have enabled the development of nanoscale sensors that outperform conventional biosensors. This review summarizes the nanoscale biosensors that use aptamers as molecular recognition elements. The advantages of aptamers over antibodies as sensors are highlighted. These advantages are especially apparent with electrical sensors such as electrochemical sensors or those using field-effect transistors. FigureFeeling proteins with aptamer-functionalized carbon nanotubes

Photoconductivity and enhanced memory effects in hybrid C60–graphene transistors

We describe the observation of photoconductivity and enhanced memory effects in graphene devices functionalized with clusters of alkylated C(60) molecules. The alkylated C(60) clusters were adsorbed on chemical vapor deposition-grown graphene devices from an aprotic medium. The resulting alkylated C(60)-graphene hybrid devices showed reproducible photoconductive behavior originating from the electron-accepting nature of the C(60) molecules. Significantly enhanced gate hysteresis was observed upon illumination with visible light, thereby enabling the use of C(60)-graphene hybrid devices in three-terminal photo-memory applications.

Interface charge induced p-type characteristics of aligned Si(1-x)Gex nanowires.

This study reports the electrical transport characteristics of Si(1-x)Gex (x=0-0.3) nanowires. Nanowires with diameters of 50-100 nm were grown on Si substrates. The valence band spectra from the nanowires indicate that energy band gap modulation is readily achievable using the Ge content. The structural characterization showed that the native oxide of the Si(1-x)Gex nanowires was dominated by SiO2; however, the interfaces between the nanowire and the SiO2 layer consisted of a mixture of Si and Ge oxides. The electrical characterization of a nanowire field effect transistor showed p-type behavior in all Si(1-x)Gex compositions due to the Ge-O and Si-O-Ge bonds at the interface and, accordingly, the accumulation of holes in the level filled with electrons. The interfacial bonds also dominate the mobility and on- and off-current ratio. The large interfacial area of the nanowire, together with the trapped negative interface charge, creates an appearance of p-type characteristics in the Si(1-x)Gex alloy system. Surface or interface structural control, as well as compositional modulation, would be critical in realizing high-performance Si(1-x)Gex nanowire devices.

Air-stable n-type operation of Gd-contacted carbon nanotube field effect transistors

We report air-stable n-type operations of the single-walled carbon nanotube field effect transistors (SWNT-FETs) fabricated with Gd electrodes. Unlike previously reported n-type SWNT-FETs, our devices maintained their n-type operation characteristics in ambient atmosphere for more than two months. The shallow Gd films with a thickness below 20 nm are corroded by environmental oxygen, whereas the well-contacted Gd-SWNT interfaces underneath the thick Gd layers are protected from contaminations by air molecules. Theoretical studies based on the first-principles electronic structure calculations confirm that Gd layers have an excellent binding affinity to the SWNTs.

On-Chip Electrical Breakdown of Metallic Nanotubes for Mass Fabrication of Carbon-Nanotube-Based Electronic Devices

A mass fabrication scheme for carbon-nanotube (CNT)-based electronic devices is developed by combining the semiconductor wafer electrical sorting with selective burning of metallic CNT wires. By applying a millisecond electrical pulse to CNTs with the optimized logical scheme of voltage stress, we successfully removed the metallic CNTs but not the high-performance semiconductor CNTs. The fabrication scheme implemented with a probe card achieved a 100 % gross yield of CNT-based sensors with a short process time.

Positioning of the Fermi level in graphene devices with asymmetric metal electrodes

To elucidate the effect of the work function on the position of the Dirac point, we fabricated graphene devices with asymmetric metal contacts. By measuring the peak position of the resistance for each pair of metal electrodes, we obtained the voltage of the Dirac point VgDirac (V) from the gate response. We found that the position of VgDirac (V) in the hybrid devices was significantly influenced by the type of metal electrode. The measured shifts in VgDirac (V) were closely related to the modified work functions of the metal-graphene complexes. Within a certain bias range, the Fermi level of one of the contacts aligned with the electron band and that of the other contact aligned with the hole band.

The Brevibacterium albidum gene encoding the arginine tRNACCG complements the growth defect of an Escherichia coli strain carrying a thermosensitive mutation in the rnpA gene at the nonpermissive temperature

Abstract The Escherichia colirnpA gene encodes C5 protein, the protein component of RNase P. The rnpA49 mutation renders the C5 protein thermosensitive, which results in thermosensitivity of RNase P function. The chromosomal DNA region from Brevibacterium albidum that complements the rnpA49 mutation was analysed. The gene capable of complementing the growth defect of an rnpA49 mutant strain at nonpermissive temperature was identified as the gene for an arginine tRNA with anticodon CCG by a deletion analysis combined with complementation assays. Transcription of the arginine tRNA gene carried on a multicopy plasmid was correlated with the complementation of the rnpA49 mutation, indicating that the gene product is indeed responsible for complementation of the rnpA49 mutation.

Electrical sorting of carbon nanotube transistors for mass-producible bio-sensors

This paper reports useful fabrication scheme customized for biosensing application by adopting the Collins approach of electrical breakdown (Collins, 2001) with some modification to improve the fabrication cost and reduce fabrication time.The electrical breakdown scheme was modified to increase the yield of electrical sorting and reduce sorting time, which is very important in real mass-production. CNTFETs were fabricated using the patterned catalyst growth technique, and source and drain electrodes were defined using photolithography and lift-off process. Then electrical sorting was performed in ambient condition.

Fabrication of Si 1-x Ge x alloy nanowire FETs

We have fabricated field effect transistors (FETs) by using high quality Si_1-xGe_x alloy nanowires. To obtain stable contacts between Si_1-xGe_x alloy nanowire and Ni/Au electrodes, we annealed the samples at 300 degC furnace with Ar atmosphere or RTA at 400 X2. |4| Three different Si_1-xGe_x alloy nanowires (x=5, 15, 30) were used for the fabrication of field effect transistors, and p-type gating effect observed from Si_1-xGe_x alloy nanowire devices. Among them, pronounced p-type transistor behavior, with on/off ratios as high as 106 observed from Si_0.7Ge_0.3 nanowire field effect transistor.