纳米线多型异质结碳化硅室温单电子晶体管研究

采用碳化硅4H/6H多型纳米线制备单电子晶体管,在室温下观察到库仑阻塞效应和负微分电阻,I-V曲线呈现典型的库仑台阶,其台阶为周期性的,这些周期性小台阶,又呈现非周期的嵌套结构。单根纳米线碳化硅由4H/6H多型交替生长构成,它们嵌合构成竹节状生长,碳化硅多型结构中4H多型晶体构成双势垒,其直径为10~80nm,长度约50nm。而联结4H多型的6H多型晶体部分,长度约20nm,且直径较细(约10~35nm),被认为是库仑孤岛。

Enhanced photoluminescence of a microporous quantum dot color conversion layer by inkjet printing

Owing to their high color purity,tunable bandgap,and high efficiency,quantum dots(QDs)have gained significant attention as color conversion materials for high-end display applications.Moreover,inkjet-printed QD pixels show great potential for realizing full-color mini/micro-light emitting diode(micro-LED)-based displays.As a color conversion layer,the photoluminescence intensity of QDs is limited by the insufficient absorptance of the excitation light due to the lack of scattering.Conventional scatterers,such as titanium dioxide microparticles,have been applied after additional surface engineering for sufficient dispersity to prevent nozzle clogging in inkjet printing process.In our work,as an alternative approach,we use inkjet printing for depositing a phase separating polymer ink based on polystyrene(PS)and polyethylene glycol(PEG).QD/polymer composite pixels with scattering micropores are realized.The morphology of the micropores can be tailored by the weight ratio between PS and PEG which enables the manipulation of scattering capability.With the presence of the microporous structure,the photoluminescence intensity of the QD film is enhanced by 110%in drop-cast films and by 35.3%in inkjet-printed QD pixel arrays compared to the reference samples.

Pyrolysis-induced shrinking of threedimensional structures fabricated by twophoton polymerization:experiment and theoretical model

The introduction of two-photon polymerization(TPP)into the area of Carbon Micro Electromechanical Systems(CMEMS)has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV lithography.Pyrolysis of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with accuracy.In this work,we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900℃.Through this process,photoresist microwires thermally decompose and shrink by as much as 75%,resulting in glassy carbon nanowires with linewidths between 300 and 550 nm.Even after the thermal decomposition induced by the pyrolysis step,the linewidth of the carbon nanowires was found to be dependent on the TPP exposure parameters.We have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires,but also in buckling in the case of slender carbon nanowires(for aspect ratios greater than 30).Furthermore,we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires,a trend that is consistent with several works found in the literature.This phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures,serving as a simple guideline for shrinkage evaluation in other designs.

Fully printed origami thermoelectric generators for energy-harvesting

Energy-harvesting from low-temperature environmental heat via thermoelectric generators(TEG)is a versatile and maintenancefree solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things(IoT)that require an independent wireless power supply.A prerequisite for market competitiveness,however,is the costeffective and scalable manufacturing of these TEGs.Our approach is to print the devices using printable thermoelectric polymers and composite materials.We present a mass-producible potentially low-cost fully screen printed flexible origami TEG.Through a unique two-step folding technique,we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material.We realize a device architecture with a high thermocouple density of 190 per cm2 by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8μWcm^(−2)from a 30 K temperature difference.The device properties are adjustable via the print layout,specifically,the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source.We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.

Monolithically printed all-organic flexible photosensor active matrix

Upcoming technologies in the fields of flexible electronics require the cost-efficient fabrication of complex circuitry in a streamlined process.Digital printing techniques such as inkjet printing can enable such applications thanks to their inherent freedom of design permitting the mask-free deposition of multilayer optoelectronic devices without the need for subtracting techniques.Here we present an active matrix sensor array comprised of 100 inkjet-printed organic thin film transistors(OTFTs)and organic photodiodes(OPDs)monolithically integrated onto the same ultrathin substrate.Both the OTFTs and OPDs exhibited high-fabrication yield and state-of-the-art performance after the integration process.By scaling of the OPDs,we achieved integrated pixels with power consumptions down to 50 nW at one of the highest sensitivities reported to date for an all-organic integrated sensor.Finally,we demonstrated the application potential of the active matrix by static and dynamic spatial sensing of optical signals.

Origami-inspired perovskite X-ray detector by printing and folding

X-ray detectors are of pivotal importance for the scientific and technological progress in a wide range of medical,industrial,and scientific applications.Here,we take advantage of the printability of perovskite-based semiconductors and achieve a high X-ray sensitivity combined with the potential of an exceptional high spatial resolution by our origami-inspired folded perovskite X-ray detector.The high performance of our device is reached solely by the folded detector architecture and does not require any photolithography.The design and fabrication of a foldable perovskite sensor array is presented and the detector is characterized as a planar and as a folded device.Exposed to 50 kVp−150 kVp X-ray radiation,the planar detector reaches X-ray sensitivities of 25−35μC/(Gyaircm^(2)),whereas the folded detector achieves remarkably increased X-ray sensitivities of several hundredμC/(Gyaircm^(2))and a record value of 1409μC/(Gyaircm^(2))at 150 kVp without photoconductive gain.Finally,the potential of an exceptional high spatial resolution of the folded detector of more than 20 lp/mm under 150 kVp X-ray radiation is demonstrated.