Electrochemical pore formation in Si using an anodized needle electrode was studied. In the electrochemical process, a Pt, Ir or Pd needle with a diameter of 50-200 μm was brought into contact at its tip with a Si wafer, which was not connected to an external circuit, in HF solution. By applying an anodic potential to the needle electrode against a Pt counter electrode, a pore with a diameter slightly larger than the diameter of the needle electrode was formed in both p-type and n-type Si, of which current efficiency was higher for n-type Si. Through-holes were electrochemically formed in p-type and n-type Si wafers at speeds higher than 30 μm min(-1) using a sharpened Ir needle electrode. A model was proposed to explain the results, in which the pore formation was attributed to successive dissolution of Si atoms near the 3-phase (Si/metal/HF solution) boundary by positive holes injected from the needle electrode to the surface of Si.
Transposable elements (TEs) are DNA fragments that have the ability to move from one chromosomal location to another. The insertion of TEs into gene-rich regions often affects changes in the expression of neighboring genes. Miniature Ping (mPing) is an active miniature inverted-repeat TE discovered in the rice genome. It has been found to show exceptionally active transposition in a few japonica rice varieties, including Gimbozu, where mPing insertion rendered adjacent genes stress-inducible. In the Gimbozu population, it is highly possible that several genes with modified expression profiles are segregating due to the de novo mPing insertions. In our study, we utilized a screening system for detecting de novo mPing insertions in the upstream region of target genes and evaluated the effect of mPing on the stress response of the target genes. Screening for 17 targeted genes revealed five genes with the mPing insertion in their promoters. In most cases, the alteration of gene expression was observed under stress conditions, and there was no change in the expression levels of those five genes under normal conditions. These results indicate that the mPing insertion can be used as a genetic tool to modify an expression pattern of a target gene under stress conditions without changing the expression profiles of those under natural conditions.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9885-1) contains supplementary material, which is available to authorized users.
Scaling of semiconductor devices has caused nano-structure stiction issues during the drying step of wafer cleaning. We have already proposed a surface modification process to reduce the surface energy, and we have demonstrated this process is more effective for preventing nano-structure stiction than conventional IPA (isopropyl alcohol) drying. In this paper, the proper molecular structure is investigated for surface modification agents. It is important for the suppression of stiction to reduce a surface free energy rather than to increase a water contact angle. We have attained stiction free drying of a high aspect ratio pattern with 15 nm half pitch line and space using agents with shorter alkyl groups.
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