Narrow Results

During these last years, the substantially biological field effect transistors (BioFET) are one of the most abundant classes of electronic sensors for biomolecular detection. The determination of glucose levels using these biosensors, especially in the medical diagnosis and food industries, is gaining popularity. Among them, ion-sensitive field effect transistor (ISFET) is considered one of the most intriguing approaches in electrical biosensitivity technology. The glucose sensor ISFET detects the glucose molecule by catalyzing glucose to gluconic acid and hydrogen peroxide in the presence of oxygen. In this paper, first of all we examine some of the main advantages in this field, the perspective of applications and the main issues in order to stimulate a broader interest in the development of biosensors based on ISFET and to extend their applications for a reliable and sensitive glucose analysis. Thereafter, a biosensor with field effect sensitive to the ions for the detection of glucose is modeled analytically. In the proposed model, the glucose concentration is presented according to the gate voltage. The simulated data show that the analytical model can be used with an electrochemical glucose sensor to predict mechanism’s behavior of detection in the biosensors.

An analytical model of the channel electron energy distribution in an on-state GaN transistor has been proposed based on the assumption that drift velocities of channel electrons obey the two-dimensional Maxwell–Boltzmann distribution. The validity of such an assumption was confirmed by Monte Carlo simulation. It was found that there could be a larger number of high-energy channel electrons whose energy is higher than the intervalley energy between ${\mathrm{\Gamma }}_1$ and ${\mathrm{\Gamma }}_2$ valleys in a GaN transistor with a high electron temperature. The fraction of hot electrons with its energy higher than the intervalley energy between ${\mathrm{\Gamma }}_1$ and ${\mathrm{\Gamma }}_2$ valleys to the total channel electrons can easily reach 50% when the electron temperature is higher than 3000 K. Such an electron temperature in a GaN transistor had been determined in experiments. Thus, hot electrons in the ${\mathrm{\Gamma }}_1$ valley can transit into ${\mathrm{\Gamma }}_2$ valleys. It suggests that intervalley transitions could be one possible physical origin of the abrupt change in the source−drain current in GaN devices. The proposed model can well explain how an abrupt change in the source–drain current in GaN transistor experiments depends on the voltage-dependent gate, the trap, etc.

Solvent vapor atmosphere is introduced for solution-evaporated poly(3-hexylthiophene) (P3HT) formation in fabricating organic field-effect transistors (OFETs). As changing the solvent vapor atmosphere, prominent influences on the assemblies of P3HT nanowires during solidification were represented, leading to the difference in nanostructure morphologies. We demonstrated that the device fabricated under anisole solvent vapor atmosphere is superior in electrical performance to that of the devices fabricated under other conditions. In this process, anisole solvent vapor atmosphere transparently facilitated one-dimensional (1D) self-assembly through π–π stacking interaction among the P3HT units during solidification.

Single-walled carbon nanotubes (SWCNTs) with incovalently attached iodine, were obtained by physical absorption. The different diameter sizes of SWCNTs, with different numbers of iodine molecule, enhance the density contrast between them which becomes evident in density gradient ultracentrifugation (DGU) targeted to sort certain species of SWCNTs. The results of optical absorbance and photoluminescence emission showed that iodine-assisted DGU preferentially separates semiconducting nanotubes with certain diameters [(6, 5), (7, 5), (8, 4), and (7, 6)].We have applied these semiconducting, species enriched SWCNTs to prepare solution-processed field effect transistor (FET) devices with random nanotube network active channels. The devices exhibit stable p-type semiconductor behavior in air with very promising characteristics. The on-off current ratio reaches up to 2 × 10⁴ within a narrow window of voltage (-10 V to 10 V), and estimated hole mobility of 21.7 cm² V^-1 s^-1.