The most effective and potential approach to improve the performance of heterojunction photodetectors is to obtain favorable interfacial passivation by adding an insertion layer. In this paper, MoO
x
/Al2O3/n-Si heterojunction photodetectors with excellent photocurrents, responsivity and detectivity were fabricated, in which alumina acts as a tunneling passivation layer. By optimizing the post-annealing treatment temperature of the MoO
x
and the thickness of the ultra-thin Al2O3, the photodetector achieved a ratio of photocurrent to dark current of 3.1 × 105, a photoresponsivity of 7.11 A W−1 (@980 nm) and a detective of 9.85 × 1012 Jones at −5 V bias. Besides, a self-driven response of 0.17 A W−1 and a high photocurrent/dark current ratio of 2.07 × 104 were obtained. The result demonstrated that optimizing the interface of heterojunctions is a promising way to obtain a heterojunction photodetector with high-performance.
Indium oxide (In2O3) has been reported
widely
due to its good optical properties and stability in optoelectronics
and other fields. However, it is difficult to realize thickness control
of atomically thin In2O3, which will confine
the use of In2O3 films. Here, we report a simple
and precise method to synthesize thickness-controllable In2O3 films using printed oxide skin of liquid metals. The
cleaning processes were investigated to remove the metal residues
on the films. It was found that liquid metal washing and annealing
procedures could remove the residues without damaging the films and
thus improve the uniformity. At the same time, the thickness of In2O3 films was controlled by adjusting the oxygen
concentration of the atmosphere. Furthermore, the band gap regulation
of indium oxide was realized by adjusting the thickness, which provided
a good basis for the selenization of oxide films.
Flexible
photodetectors are considered to be extremely important
flexible electronic components of the future. In this work, flexible
silicon (F-Si) substrates with inverted pyramidal light-trapping structures
were prepared by wet chemistry and metal-assisted etching. Due to
the better ability of the light-trapping structure to capture light,
the F-Si substrate was capable of absorbing more than 90% of visible
light and can be in bending angles of over 180°. On the basis
of F-Si substrates with light-trapping structures, self-powered MoO3/n-Si heterojunction flexible photodetectors (FPDs) were prepared
to achieve high responsivity (0.696 A/W@980 nm), detectivity (1.59
× 1013 jones), and fast response (τr/τd of 5.35 μs/0.97 μs). The devices
also showed effective photoresponse in the wavelength range from 405
to 980 nm. Moreover, the Si-based FPDs exhibited a favorable response
to high-frequency light, with a response frequency of up to 100 kHz.
The photocurrent of the device maintained more than 95% of the initial
value after 200 bending cycles. In addition, Si-based FPDs are successfully
applied to fingertip heartbeat tests for human health data extraction.
The development of Si-based FPDs provides a path for flexible electronic
devices.
Vertical
graphene nanowalls (VGNs) with excellent heat-transfer
properties are promising to be applied in the thermal management of
electronic devices. However, high growth temperature makes VGNs unable
to be directly prepared on semiconductors and polymers, which limits
the practical application of VGNs. In this work, the near room-temperature
growth of VGNs was realized by utilizing the hot filament chemical
vapor deposition method. Catalytic tantalum (Ta) filaments promote
the decomposition of acetylene at ∼1600 °C. Density functional
theory calculations proved that C2H* was the main active
carbon cluster during VGN growth. The restricted diffusion of C2H* clusters induced the vertical growth of graphene nanoflakes
on various substrates below 150 °C. The direct growth of VGNs
successfully realized the excellent interfacial contact, and the thermal
contact resistance could reach 3.39 × 10–9 m2·K·W–1. The temperature of electronic
chips had a 6.7 °C reduction by utilizing directly prepared VGNs
instead of thermal conductive tape as thermal-interface materials,
indicating the great potential of VGNs to be directly prepared on
electronic devices for thermal management.
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