Top-gated and bottom-gated transistors with multilayer MoS channel fully encapsulated by stacked AlO/HfO (9 nm/6 nm) were fabricated and comparatively studied. Excellent electrical properties are demonstrated for the TG transistors with high on-off current ratio of 10, high field-effect mobility of 10 cm V s, and low subthreshold swing of 93 mV dec. Also, enhanced reliability has been achieved for the TG transistors with threshold voltage shift of 10-10 V MV cm after 6 MV cm gate-biased stressing. All improvement for the TG device can be ascribed to the formed device structure and dielectric environment. Degradation of the performance for the BG transistors should be attributed to reduced gate capacitance density and deteriorated interface properties related to vdW gap with a thickness about 0.4 nm. So, the TG transistor with MoS channel fully encapsulated by stacked AlO/HfO is a promising way to fabricate high-performance ML MoS field-effect transistors for practical electron device applications.

For top-gated MoS 2 field-effect transistors, damaging the MoS 2 surface to the MoS 2 channel are inevitable due to chemical bonding and/or high-energy metal atoms during the vacuum deposition of gate dielectric, thus leading to degradations of field-effect mobility (μ FE ) and subthreshold swing (SS). A top-gated MoS 2 transistor is fabricated by directly transferring a 9 nm mica flake (as gate dielectric) onto the MoS 2 surface without any chemical bonding, and exhibits excellent electrical properties with an on-off ratio of ∼10 8 , a low threshold voltage of ∼0.2 V, a record μ FE of 134 cm 2 V −1 s −1 , a small SS of 72 mV dec −1 and a low interface-state density of 8.8×10 11 cm −2 eV −1 , without relying on electrode-contact engineered and/or phase-engineered MoS 2 . Although the equivalent oxide thickness of the mica dielectric is in the sub-5 nm regime, enhanced stability characterized by normalized threshold voltage shift (1.2×10 −2 V MV −1 cm −1 ) has also been demonstrated for the transistor after a gate-bias stressing at 4.4 MV cm −1 for 10 3 s. All these improvements should be ascribed to a damage-free MoS 2 channel achieved by a dry transfer of gate dielectric and a clean and smooth surface of the mica flake, which greatly decreases the charged-impurity and interface-roughness scatterings. The proposed transistor with low threshold voltage and high stability is highly desirable for lowpower electronic applications.

Few-layered molybdenum disulfide (MoS2) has demonstrated promising advantages for the integration of next-generation electronic devices. A vertical short-channel MoS2 transistor with a channel length of sub-10 nm can be realized using mica as the insulated mesa and MoS2 flake dry-transferred onto the mica as the channel. A near-perfect symmetrical and fully saturated output characteristic can be obtained for the positive or negative drain–source voltage. This result is attributed to an effective transformation of the drain–source electrode contact from Schottky contact to Ohmic contact via forming gas annealing. The vertical-channel MoS2 transistor with a channel length of 8.7 nm exhibits excellent electrical characteristics, for example, a negligible hysteresis voltage of 60 mV, an extraordinarily small subthreshold swing of 73 mV/dec, a considerably weakened drain-induced barrier-lowering effect (100 mV/V), and the first-reported intrinsic delay time of 2.85 ps. Moreover, a logic inverter can be realized using the two vertical-channel MoS2 transistors, with a high voltage gain of 33. Experimental results indicate that the developed method is a potential approach for fabricating MoS2 transistors with an ultrashort channel and high performance, and consequently, manufacturing MoS2-based integrated circuits.

To avoid surface damage of a MoS 2 channel, a mica flake with high permittivity and atomically flat surface was dry transferred onto a multilayer MoS 2 flake to prepare top-gated transistors. For the first time, the interface properties of mica/MoS 2 and the long-term stability of devices were investigated when the transistors were exposed to ambient air. Results show that the electrical performance of the transistors is degraded significantly when the devices are exposed to ambient moisture for a long time, due to the strong hydrophilism of mica. The transfer curves of the transistors cannot be recovered to their initial states even after annealing. The adsorbed moisture can become trapped at the interface between the MoS 2 channel and mica dielectric or on the MoS 2 surface, resulting in enhanced carrier scattering and degraded device performance. However, the top-gated MoS 2 transistor with Al 2 O 3 encapsulation exhibits enhanced stability even after annealing or exposure to atmosphere for 200 days. The excellent stability should be attributed to the effective insulation of moisture from the ambient air by Al 2 O 3 encapsulation. Therefore, a dense and hydrophobic encapsulation layer is indispensable for stable and highperformance top-gated MoS 2 transistors with mica gate dielectric.

BackgroundChromosomal instability is a hallmark of cancer. Chromosomal imbalances, like amplifications and deletions, influence the transcriptional activity of genes. These imbalances affect not only the expression of genes in the aberrant chromosomal regions, but also that of related genes, and may be relevant to the cancer status.Material/MethodsHere, we used the 7 publicly available microarray studies in breast cancer tissues and propose a general and unsupervised method by using the gene expression data and related gene information to systematically identify aberrant chromosomal regions. This method aimed to identify the chromosomal regions where the genes and their related genes both show consistent changes in the expression levels. Such patterns have been reported to be associated with the chromosomal aberrations and may be used in cancer diagnosis.ResultsWe compared 488 tumor and 222 normal samples from 7 microarray-based human breast cancer studies and detected the amplifications of 8q11.21, 14q32.11, 4q21.23, 18q11.2, Xq28, and the deletions of 3p24.1, 10q23.2 (BSCG1), 20p11.21, 9q21.13, and 1q41, which may be involved in the novel mechanisms of tumorigenesis. In addition, several known pathogenic genes, transcription factors (TFs), and microRNAs (miRNAs) associated with breast cancer were found.ConclusionsThis approach can be applied to other microarray studies, which provide a new and useful method for exploring chromosome structural variations in different types of diseases.