679wileyonlinelibrary.com attractive for potential applications, such as nanoelectronic switches, [3][4][5] transistors, [ 6 ] optical devices, [ 7,8 ] and micromechanical devices. [ 9 ] VO 2 thin fi lms have been synthesized by a variety of deposition techniques, such as pulsed laser deposition (PLD), [10][11][12][13][14] molecular beam epitaxy (MBE), [ 15 ] reactive sputtering, [ 16,17 ] sol-gel processing, [ 18 ] chemical vapor deposition (CVD), [ 19 ] thermal oxidation, [ 20 ] and ion beam deposition. [ 21,22 ] Most of the studies report on VO 2 fi lms with thicknesses in the range of 40-200 nm. Sub-10 nm continuous fi lms of ≈2 nm thickness have been deposited both by PLD [ 23 ] and MBE [ 15 ] on monocrystalline TiO 2 and MITs with resistivity changes of ≈500 × and ≈25 × , respectively. However, the use of TiO 2 monocrystals as a substrate is unfavorable for practical nanoelectronic applications and PLD and MBE are not deposition techniques that are well suited for device manufacturing. By contrast, VO 2 fi lms deposited by techniques suitable for manufacturing, including atomic layer deposition (ALD), have typically been noncontinuous and have shown a strongly degraded MIT when the fi lm thicknesses were below 40-50 nm. [24][25][26] In recent years, ALD [ 27,28 ] has become the reference technique for the deposition of dielectric [ 29 ] and metallic [ 30 ] thin fi lms for nanoelectronic applications. [31][32][33] ALD is characterized by self-limiting surface reactions, which enables a precise control over fi lm thickness and stoichiometry. In addition, the high conformality allows deposition onto three-dimensional (3D) structures, as increasingly required for advanced nanoelectronic applications. However, the ALD growth of thin high quality VO 2 is not established yet. VO 2 ALD has been reported using vanadyl acetonate and O 2 [ 34 ] or VOCl 3 . [ 35 ] X-ray diffraction (XRD) indicated the presence of VO 2 and signs of MITs have been observed. Yet, these processes have not been able to achieve thin, continuous, and phase-pure fi lms. By contrast, the ALD from tetrakis(ethylmethylamino) vanadium (TEMAV) and O 3 has led to continuous smooth fi lms that show an MIT down to a thickness of ≈40 nm. [36][37][38][39] ALD VO 2 from TEMAV with H 2 O as oxygen source has been reported to lead to mixed valence VO x fi lms which can be converted to VO 2 by postannealing. [ 40 ] Nevertheless, no continuous ALD VO 2 fi lms featuring an MIT Nanoscale morphology of vanadium dioxide (VO 2 ) fi lms can be controlled to realize smooth ultrathin (<10 nm) crystalline fi lms or nanoparticles with atomic layer deposition, opening doors to practical VO 2 metal-insulator transition (MIT) nanoelectronics. The precursor combination, the valence of V, and the density for as-deposited VO 2 fi lms, as well as the postdeposition crystallization annealing conditions determine whether a continuous thin fi lm or nanoparticle morphology is obtained. It is demonstrated that the fi lms and particles possess both a structural and an electronic t...

Record-low contact resistivity (ρ c ) for n-Si, down to 1.5×10 -9 Ω•cm 2 , is achieved on Si:P epitaxial layer. We confirm that Ti silicidation reduces the ρ c for n-Si, while an additional Ge pre-amorphization implantation (PAI) before Ti silicidation further extends the ρ c reduction. In situ doped Si:P with P concentration of 2×10 21 cm -3 is used as the substrate, and dynamic surface anneal (DSA) boosts P activation. In addition, TiO x based metal-insulator-semiconductor (MIS) contact is also studied on Si:P but is found to suffer from low thermal stability.

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