Boron deficiency hampers the productivity of 132 crops in more than 80 countries. Boron is essential in higher plants primarily for maintaining the integrity of cell walls and is also beneficial and might be essential in animals and in yeast. Understanding the molecular mechanism(s) of boron transport is crucial for alleviating boron deficiency. Here we describe the molecular identification of boron transporters in biological systems. The Arabidopsis thaliana mutant bor1-1 is sensitive to boron deficiency. Uptake studies indicated that xylem loading is the key step for boron accumulation in shoots with a low external boron supply and that the bor1-1 mutant is defective in this process. Positional cloning identified BOR1 as a membrane protein with homology to bicarbonate transporters in animals. Moreover, a fusion protein of BOR1 and green fluorescent protein (GFP) localized to the plasma membrane in transformed cells. The promoter of BOR1 drove GFP expression in root pericycle cells. When expressed in yeast, BOR1 decreased boron concentrations in cells. We show here that BOR1 is an efflux-type boron transporter for xylem loading and is essential for protecting shoots from boron deficiency.

We describe a boron (B) transporter, Os BOR1, in rice (Oryza sativa). Os BOR1 is a plasma membrane-localized efflux transporter of B and is required for normal growth of rice plants under conditions of limited B supply (referred to as -B). Disruption of Os BOR1 reduced B uptake and xylem loading of B. The accumulation of Os BOR1 transcripts was higher in roots than that in shoots and was not affected by B deprivation; however, Os BOR1 was detected in the roots of wild-type plants under -B conditions, but not under normal conditions, suggesting regulation of protein accumulation in response to B nutrition. Interestingly, tissue specificity of Os BOR1 expression is affected by B treatment. Transgenic rice plants containing an Os BOR1 promoter-b-glucuronidase (GUS) fusion construct grown with a normal B supply showed the strongest GUS activity in the steles, whereas after 3 d of -B treatment, GUS activity was elevated in the exodermis. After 6 d of -B treatment, GUS activity was again strong in the stele. Our results demonstrate that Os BOR1 is required both for efficient B uptake and for xylem loading of B. Possible roles of the temporal changes in tissue-specific patterns of Os BOR1 expression in response to B condition are discussed.

Schottky barrier height modulation in metal/Ge Schottky junction was demonstrated by inserting an ultrathin interfacial silicon nitride layer. The SiN interfacial layer suppressed strong Fermi level pinning in metal/Ge Schottky junction, which resulted in effective control of Schottky barrier height. Metal/SiN/Ge Schottky diode was systematically investigated in terms of SiN thickness dependence and metal work function dependence. At an optimal SiN thickness, Ohmic contact between metal and Ge was obtained as a result of Fermi level depinning, and almost ideal Schottky barrier height determined by the work function difference between the metal and Ge was achieved. This technology was finally applied to metal source/drain Ge metal-oxide-semiconductor field-effect-transistors with low source/drain resistance.

The roles of three membrane proteins, BOR1, DUR3, and FPS1, in boron (B) transport in yeast were examined. The boron concentration in yeast cells lacking BOR1 was elevated upon exposure to 90 mM boric acid, whereas cells lacking DUR3 or FPS1 showed lower boron concentrations. Compared with control cells, cells overexpressing BOR1 or FPS1 had a lower boron concentration, and cells overexpressing DUR3 had a higher boron concentration. These results suggest that, in addition to the efflux boron transporter BOR1, DUR3 and FPS1 play important roles in regulating the cellular boron concentration. Analysis of the yeast transformants for tolerance to a high boric acid concentration revealed an apparent negative correlation between the protoplasmic boron concentration and the degree of tolerance to a high external boron concentration. Thus, BOR1, DUR3, and FPS1 appear to be involved in tolerance to boric acid and the maintenance of the protoplasmic boron concentration.

The effects of quantum confinement on transport properties of silicon nanowire metal-oxide-semiconductor field-effect transistors (FETs) and single-electron transistors are experimentally investigated. By carefully designing the channel width, the nanowire transistors operate as silicon nanowire FETs (SNWFETs) or single-charge transistors. Large quantum confinement in ultranarrow silicon nanowires plays a key role in these devices. We also adopt a special device configuration in which both n-type and p-type operations can be attained in an identical device, and the dependence on the channel direction and charge polarity is intensively investigated. Statistical measurements and band structure calculation reveal that [110] p-channel SNWFETs show smaller threshold voltage variations and [100] single-hole transistors show the largest Coulomb blockade oscillations at room temperature.

Organic or carbon semiconductor devices are promising for both nanoelectronic and macroelectronic applications. One of the major challenges to achieve high performance of these devices lies on understanding and improving the metal-organic ͑M/O͒ interface. In this paper, we present evidence and demonstration of Fermilevel depinning at the M/O interface by inserting an ultrathin interfacial Si 3 N 4 insulator in between. The M/O contact behavior is successfully tuned from rectifying to quasi-Ohmic and to tunneling by varying the Si 3 N 4 thickness within 0-6 nm. Detailed physical mechanisms of Fermi-level pinning/depinning responsible for the M/O contact behavior are clarified based on a lumped-dipole model and a simple depinning model. This work sheds light on the fundamental understanding of the M/O interface properties and also proves a practical engineering method of achieving low-resistance quasi-Ohmic contacts for organic electronic devices.

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We have fabricated and demonstrated ultrathin In-Ga-Zn-O (IGZO) channel ferroelectric HfO2 field effect transistor (FET) with memory operation. Ultrathin-body IGZO ferroelectric FET (FeFET) shows high mobility and nearly ideal subthreshold slop with minimum 8 nm channel thickness, thanks to the properties of IGZO material, junctionless FET operation, nearly-zero low-k interfacial layer on metal-oxide channel and effective capping for realizing ferroelectric phase formation with HfZrO2 (HZO). The controllable memory operations are achieved with the use of back gate. The design guideline of IGZO FeFET is proposed by discussing the thickness of front gate oxide HZO and back gate oxide SiO2 using TCAD simulation. The material and electrical properties of metal/HZO/IGZO/metal capacitor are also investigated. Metal/HZO/IGZO/metal capacitor has up to 10 8 endurance and over one-year retention. IGZO FeFET shows a potential for high-density and low-power memory application.