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    The enhancement of sensitivity and response times of PDMS-based capacitive force sensor by means of active layer modification
    (2021-06-01)
    Siangkhio, Yasumin
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    Jessadaluk, Sukittiya
    In this work, sensitivity and response times of PDMS-based capacitive force sensors are enhanced via the modifications of the PDMS layer. Two modifying approaches are proposed; (i) change PDMS's (elastomer:curing agent) ratio and (ii) adding conductive polymer PEDOT:PSS into the PDMS layer. The change of PDMS (elastomer:curing agent) ratio from (10:1) to (30:1) increases the sensitivity from 0.4 0.08 to 0.72 0.23 kPa-1 (+80%) but it does not significantly affect the response/recovery times. In addition, by adding 1% wt. of PEDOT:PSS to PDMS (30:1), the further increment of sensitivity from 0.72 0.23 to 1.44 0.17 kPa-1 (+100%) and the shorter response time from 1.59 0.02 to 0.45 0.03 s (-72%) are observed. The mechanical and electrical studies reveal that the change of PDMS (elastomer:curing agent) ratio and the adding of PEDOT:PSS to PDMS layer result in the modification of PDMS's deformability and the increase of charge transportation, leading to the enhancement of sensing characteristics of the sensors.
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    Study on optical and electronic properties of Sn-doped ZnPc
    (2013-10-29) ;
    Sributr, Chaloempol
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    Rojanasuwan, Sunit
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    Sn doped ZnPc films were deposited on intrinsic Si and glass substrates by organic source thermal co-evaporation technique with different deposition rates. Optical properties and electronic structure were characterized by UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) respectively. The UV-Vis results showed that phase transition of ZnPc from α- phase to β-phase occurred when Sn:ZnPc deposition rate is 0.3:0.7 or higher. XPS results indicated that the outer s electron of Sn atom is transferred to the ZnPc. Broadening of the C 1s spectra is observed with the increasing of Sn deposition rate. This broadening corresponds to the change of molecular environment surrounding carbon atoms in the Sn-doped ZnPc films. © (2013) Trans Tech Publications, Switzerland.
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    Study of optical and electrical properties of tin doped cobalt-phthalocyanine thin films prepared by thermal co-evaporation
    (2018-09-05) ;
    Jessadaluk, Sukittaya
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    ; ;
    The aim of this research is to study the specific properties e.g. surface morphology, optical absorption as well as electrical conductivity of tin-doped cobalt-phthalocyanine (CoPc) thin film prepared by thermal co-evaporation. The concentration of tin metal dopant is controlled via evaporation rate during film's preparation. The change of tin quantity leads to the significant changes not only in morphology but also in molecular packing of the doped films. Moreover, the dramatic increase in both carrier mobility and carrier concentration should provide the enhancement in electrical conductivity of the doped films. By controlling the specific properties of the tin-doped CoPc thin film, the increasing efficiency of optoelectronic applications based on metal-phthalocyanine could be achieved.
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    Influence of Antimony Species on Electrical Properties of Sb-Doped Zinc Oxide Thin Films Prepared by Pulsed Laser Deposition
    (2023-06-01)
    Jessadaluk, Sukittaya
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    This study systematically investigates the influence of antimony (Sb) species on the electrical properties of Sb-doped zinc oxide (SZO) thin films prepared by pulsed laser deposition in an oxygen-rich environment. The Sb species-related defects were controlled through a qualitative change in energy per atom by increasing the Sb content in the Sb<inf>2</inf>O<inf>3</inf>:ZnO-ablating target. By increasing the content of Sb<inf>2</inf>O<inf>3</inf> (wt.%) in the target, Sb<sup>3+</sup> became the dominant Sb ablation species in the plasma plume. Consequently, n-type conductivity was converted to p-type conductivity in the SZO thin films prepared using the ablating target containing 2 wt.% Sb<inf>2</inf>O<inf>3</inf>. The substituted Sb species in the Zn site (Sb<inf>Zn</inf><sup>3+</sup> and Sb<inf>Zn</inf><sup>+</sup>) were responsible for forming n-type conductivity at low-level Sb doping. On the other hand, the Sb–Zn complex defects (Sb<inf>Zn</inf>–2V<inf>Zn</inf>) contributed to the formation of p-type conductivity at high-level doping. The increase in Sb<inf>2</inf>O<inf>3</inf> content in the ablating target, leading to a qualitative change in energy per Sb ion, offers a new pathway to achieve high-performing optoelectronics using ZnO-based p–n junctions.
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    Enhancement of sensing characteristics of Polydimethylsiloxane-based capacitive force sensor by introducing conductive polymer to dielectric layer
    (2021-01-01)
    Siangkhio, Yasumin
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    ; ; ;
    Jessadaluk, Sukittaya
    A capacitive force sensor is one of the electronics components used in several electronic devices and applications. An improvement of sensing characteristics of the sensor, for example sensitivity and response time, becomes an interesting research topic. The alternative approach to enhance the sensitivity and response time of polydimethylsiloxane-based capacitive force sensors is proposed by introducing poly(3,4-ethylenedioxythiophene) polystyrene sulphonate, a conductive polymer, into polydimethylsiloxane active layer. Two sensors using different active layers, (i) polydimethylsiloxane (conventional sensor) and (ii) poly(3,4-ethylenedioxythiophene) polystyrene sulphonate mixed polydimethylsiloxane (modified sensor), were fabricated and characterised to reveal the sensing enhancement. Interestingly, the modified sensor shows the significant increase in the sensitivity from 0.7 to 1.14 kPa<sup>–1</sup> (+62.86%) and the shortening response time from 1.55 to 0.43 s (−72.26%) with respect to the conventional sensor. In addition, the deterioration in elastic behaviour and the faster charge–discharge behaviour observed from the poly(3,4-ethylenedioxythiophene) polystyrene sulphonate mixed polydimethylsiloxane film indicate the better deformation and charge transport than that from polydimethylsiloxane film. Therefore, it can be concluded that the conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate additive plays the role of mechanical and electrical modification of the polydimethylsiloxane active layer leading to the enhancement in sensitivity and response time of the polydimethylsiloxane-based capacitive force sensor.
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    Growth and characterizations of tin-doped nickel-phthalocyanine thin film prepared by thermal co-evaporation as a novel nanomaterial
    The aim of this research is to control specific properties of nickel-phthalocyanine (NiPc) thin film by doping with tin (Sn). The hybrid thin films, Sn-doped NiPc, were fabricated by thermal co-evaporation as a function of Sn concentration. The quantity of Sn in NiPc matrix was controlled via the different deposition rate between Sn and NiPc. The specific properties of the hybrid films, e.g. morphology, optical absorption, chemical bonding as well as electrical characteristics of the devices used such hybrid material as an active layer were characterized by combinations of microscopic and spectroscopic techniques. The experimental results evidently present the modification of thin film properties by adding Sn into NiPc matrix, i.e. the change of morphology from granules to fibers, the increase of beta-phase formation in the films as well as the enhancement of electrical properties resulting from the increase of both charge carrier mobility and carrier concentration in the hybrid material. Moreover, the internal formation of the Sn-doped NiPc reveals that Sn dopants are embedded in the NiPc matrix as Sn metal clusters coated with derivative metal oxide of Sn (SnO<inf>x</inf>). This research demonstrates that the doping metal-phthalocyanine with metal is an alternative approach to control the specific properties that possibly suit for organic electronic applications.