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The electrical contact resistance between a metal and semiconductor is one of the keys to improving the output performance of thin-film thermoelectric devices. Herein, we reduced the interface contact resistance by controlling the surface energy of a Sb2Te3semiconductor via tuning of the crystallization and orientation, preparing an intrinsically compact and flat Sb2Te3film with high surface energy and low roughness, which can give rise to a low average specific contact resistivity (8.2 × 10–6Ω cm2) with a Ni/Cu metal. The improvement in interface electrical properties is due to the increase in the surface energy and decrease in the surface roughness of the semiconductor surface, which lead to a transformation from three-dimensional island-shaped nucleation to two-dimensional layered nucleation for surface-attached metal films, forming a longitudinally tight connection contact with a low resistance. This approach allows the resistivity to become close to the fundamental theoretically calculated limit. Our work provides a new idea for reducing the contact resistivity of thin-film thermoelectric devices, which is conducive to supporting the development of thermoelectric semiconductor planarization.

Design of composites with ordered fillers arrangement results in anisotropic performances with greatly enhanced properties along a specific direction, which is a powerful tool to optimize physical properties of composites. Well-aligned core–shell SiC@SiO2whiskers in poly(vinylidene fluoride) (PVDF) matrix has been achieved via a modified spinning approach. Because of the high aspect ratio of SiC whiskers, strong anisotropy and significant enhancement in dielectric constant were observed with permittivity 854 along the parallel direction versus 71 along the perpendicular direction at 20 vol % SiC@SiO2loading, while little increase in dielectric loss was found due to the highly insulating SiO2shell. The anisotropic dielectric behavior of the composite is perfectly understood macroscopically to have originated from anisotropic intensity of interfacial polarization based on an equivalent circuit model of two parallel RC circuits connected in series. Furthermore, finite element simulations on the three-dimensional distribution of local electric field, polarization, and leakage current density in oriented SiC@SiO2/PVDF composites under different applied electrical field directions unambiguously revealed that aligned core–shell SiC@SiO2whiskers with a high aspect ratio significantly improved dielectric performances. Importantly, the thermal conductivity of the composite was synchronously enhanced over 7 times as compared to that of PVDF matrix along the parallel direction at 20 vol % SiC@SiO2whiskers loading. This study highlights an effective strategy to achieve excellent comprehensive properties for high-kdielectrics.

The application of screen-printed thin-film thermoelectric (TE) devices is still in its infancy, mainly due to low TE performance of screen-printed films and especially the poor electrical transport properties. Herein, we design and prepare a high-performance screen-printed Bi2Te3film through introducing excessive Te-based nanosolder (Te-NS) to simultaneously realize the conduction channel construction and defect control. On one hand, the promoted carrier migration makes the electrical conductivity dramatically rise about 7 times, with a maximum power factor of 4.65 μW cm –1K –2. Meanwhile, the defect formation mechanism in the screen-printed Bi2Te3film after the introduction of Te-NS is also in-depth studied, and the bipolar conduction is reduced by increased generation of TeBi•and/or more suppression of BiTe′, resulting in a postponed temperature of the maximum Seebeck coefficient. Hence, the large engineering power factor is achieved with excellent temperature linearity, indicating a possibility of screen-printed film application in a large temperature region. A TE device with a single leg has been fabricated to further demonstrate the generation validity. An open-circuit voltage of 11.34 mV and a maximum output power of 27.1 μW at a temperature gradient of 105 K have been achieved over a wide temperature range from 303 to 478 K. This study provides a theoretical and practical basis for the performance improvement of screen-printed TE films and devices.

Micro thermoelectric devices are expected to further improve the cooling density for the temperature control of electronic devices; nevertheless, the high contact resistivity between metals and semiconductors critically limits their applications, especially in chip cooling with extremely high heat flux. Herein, based on the calculated results, a low specific contact resistivity of ∼10–7Ω cm2at the interface is required to guarantee a desirable cooling power density of micro devices. Thus, we developed a generally applicable interfacial modulation strategy via localized surface doping of thermoelectric films, and the feasibility of such a doping approach for both n/p-type (Bi,Sb)2Te3films was demonstrated, which can effectively increase the surface-majority carrier concentration explained by the charge transfer mechanism. With a proper doping level, ultralow specific contact resistivities at the interfaces are obtained for n-type (6.71 × 10–8Ω cm2) and p-type (3.70 × 10–7Ω cm2) (Bi,Sb)2Te3layers, respectively, which is mainly attributed to the carrier tunneling enhancement with a narrowed interfacial contact barrier width. This work provides an effective scheme to further reduce the internal resistance of micro thermoelectric coolers, which can also be extended as a kind of universal interfacial modification technique for micro semiconductor devices.

Thermal engineering dramatically impacts the efficiency of microelectronics, but the corresponding technology lags far behind the need. For energy-efficient thermal management, a Cu–Cu2O film with highly ordered core–shell nanowire arrays and a good self-protection property was successfully fabricated using the magnetron sputtering method. The dense arrangement of nanowires in the films enhances the electronic transport property (220 mΩ sq–1), while the modified stable Cu2O layer maintained its perfect heat dissipation property, along with long-term thermal stability. The core–shell and nanogaps structure imparted an anisotropic thermal conductivity, where the out-plane electronic thermal conductivity (321 ± 16 W m–1K–1) was 33.6 times higher than the in-plane value. To study the role of anisotropic properties in heat dissipation, a boiling experiment and thermal simulation were undertaken. The Cu–Cu2O core–shell electrode was beneficial to elevate the heat transfer coefficient, which would cause a fast directional transport and reduction of interfacial superheating. We demonstrated that an advancement of microelectronics could be achieved by integrating Cu electrodes with an ordered architecture.

The contact resistance between metals and semiconductors has become critical for the design of thin-film thermoelectric devices with their continuous miniaturization. Herein, we report a novel interface tuning method to regulate the contact resistance at the Bi2Te3–Cu interface, and three Bi2Te3films with different oriented microstructures are obtained. The lowest contact resistivity (∼10–7Ω cm2) is observed between highly (00l) oriented Bi2Te3and Cu film, nearly an order of magnitude lower than other orientations. This significant decrease of contact resistivity is attributed to the denser film connections, lower lattice misfit, larger effective conducting contact area, and smaller width of the surface depletion region. Meanwhile, our results show that the reduction of contact resistance has little dependence on the interfacial diffusion based on the little change in contact resistivity after the introduction of an effective Ti barrier layer. Our work provides a new idea for the mitigation of contact resistivity in thin-film thermoelectric devices and also gives certain guidance for the size design of the next-level miniaturized devices.

We developed a universal method to prepare hydrophilic carbon nitrogen (C3N4) nanosheets. By treating C3N4nanosheets with oxygen plasma, hydroxylamine groups (N–OH) with intense protonation could be introduced on the surface; moreover, the content of N–OH groups increased linearly with the oxygen-plasma treatment time. Thanks to the excellent hydrophilicity, uniformly dispersed C3N4solution were prepared, which was further translated into C3N4paper by simple vacuum filtration. Pure C3N4paper with good stability, excellent hydrophilicity, and biocompatibility were proved to have excellent performance in tissue repair. Further research demonstrated that the oxygen-plasma treatment method can also introduce N–OH groups into other nitrogen-containing carbon materials (NCMs) such as N-doped graphene, N-doped carbon nanotube, and C2N, which offers a new perspective on the surface modification and functionalization of these carbon nanomaterials.