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Low Frequency Noise Characteristics in Multilayer MoTe2 FETs with Hydrophobic Amorphous Fluoropolymers
摘要： This paper investigates the low-frequency noise (LFN) properties of multilayer MoTe2 field effect transistors (FETs) before and after hydrophobic amorphous polymer (CYTOP) encapsulation in the subthreshold and linear regimes. Noise spectrum density of drain current (SID) shows that the low-frequency noise in multilayer MoTe2 FETs nicely fits to a 1/fγ power law with γ～1 in the frequency range of 10 Hz to 200 Hz. From the dependence of SID on the drain current, carrier number fluctuation(Δn) is considered as a dominant low frequency noise mechanism from all operation regimes in multilayer MoTe2 FETs. Extracted trap density(Nt) based on McWhorter model in this study was reduced at least more than one order level, as compared to multilayered MoTe2 FETs without CYTOP passivation.
关键词： CYTOP,1/f noise,MoTe2 FETs
更新于2025-09-23 15:23:52
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Photolithographic Patterning of Cytop with Limited Contact Angle Degradation
摘要： Cytop is a commercially available amorphous fluoropolymer with excellent characteristics including electric insulation, water and oil repellency, chemical resistance, and moisture-proof property, making it an attractive material as hydrophobic layers in electrowetting-on-dielectric (EWOD) devices. However, its highly hydrophobic surface makes it difficult for photoresists to be directly coated on the surface. To pattern Cytop, plasma treatment prior to applying photoresists is required to promote the adhesion between the photoresist and the Cytop coating. This approach inevitably causes hydrophobicity loss in the final EWOD devices. Thus, a damage-reduced recipe for Cytop patterning is urgently needed. In this paper, we first characterized the damage caused by two categories of surface treatment methods: plasma treatment and metal treatment. Parameters such as plasma gas source (Ar/O2), plasma treatment time (0–600 s), metal target (Al/Cu/Cr/Au), metal deposition process (magnetron sputtering or e-beam evaporation) were varied. Film thickness, wettability, and roughness were quantified by ellipsometry measurements, contact angle measurements, and atom force microscope (AFM), respectively. We then evaluated the effectiveness of annealing in damage reduction. Experimental results show that: (1) annealing is necessary in restoring hydrophobicity as well as smoothing surfaces; (2) specified film thickness can be obtained by controlling plasma treatment time; (3) “Ar/O2 plasma treatment + an AZ5214 soft mask + annealing” is a feasible recipe; (4) “an Al/Cu/Cr/Au hard mask + annealing” is feasible as well.
关键词： Cytop,electrowetting-on-dielectric (EWOD),annealing,patterning,microfluidics
更新于2025-09-23 15:23:52
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Simultaneous Measurement of Axial Strain, Bending and Torsion with a Single Fiber Bragg Grating in CYTOP Fiber
摘要： This paper presents the development of a 3-D displacement sensor based on one fiber Bragg grating (FBG). In order to obtain higher sensitivity and dynamic range, the FBG is inscribed in low-loss, multimode, cyclic transparent amorphous fluoropolymers (CYTOP) using the direct-write, plane-by-plane femtosecond laser inscription method. The proposed sensor is based on the influence of each displacement condition, namely axial strain, torsion and bending on the FBG reflection spectrum. Such influence is analyzed with respect to the FBG wavelength shift, reflectivity and full width half maximum (FWHM). The operation principle and theoretical background of the proposed approach is numerically analyzed by means of finite element analysis for the strain along the grating length and coupled-mode theory with a modified transfer matrix formulation for the FBG spectrum. The sensor is experimentally characterized and validated in which the results show good agreement between the applied axial strain, bending and torsion with relative errors below 5.5%. Thus, the proposed sensor is an interesting alternative for measuring displacements in 3-D applications such as movement analysis and the instrumentation of novel soft robots.
关键词： Polymer optical fiber,3-D displacement,fiber Bragg gratings,CYTOP
更新于2025-09-09 09:28:46