Abstract:The control of charges in a circuit due to an external electric field is ubiquitous to the exchange, storage and manipulation of information in a wide range of applications. Conversely, the ability to grow clean interfaces between materials has been a stepping stone for engineering built-in electric fields largely exploited in modern photovoltaics and opto-electronics. The emergence of atomically thin semiconductors is now enabling new ways to attain electric fields and unveil novel charge transport mechanisms… Show more
“…This process can introduce strain in the atomic lattice thus modifying the optical and electronic properties of GaSe. [9g,20] A second observation is that the number of bubbles increases in time as shown by the bottom panel of Figure d. The initial formation and growth of an individual bubble is shown in Figure e by the cross section of the AFM images taken in the region highlighted by the arrows in panel (c).…”
Section: Resultsmentioning
confidence: 87%
“…Moreover, the presence of these materials can perturb the GaSe lattice and introduce strain, which may change the photoresponse. [9g,20]…”
Gallium selenide (GaSe) is a novel 2D material, which belongs to the layered III-VIA semiconductors family and attracted interest recently as it displays single-photon emitters at room temperature and strong optical nonlinearity. Nonetheless, few-layer GaSe is not stable under ambient conditions and it tends to degrade over time. Here atomic force microscopy, Raman spectroscopy, and optoelectronic measurements are combined in photodetectors based on thin GaSe to study its long-term stability. It is found that the GaSe flakes exposed to air tend to decompose forming first amorphous selenium and Ga 2 Se 3 and subsequently Ga 2 O 3 . While the first stage is accompanied by an increase in photocurrent, in the second stage, a decrease in photocurrent is observed, which leads to the final failure of GaSe photodetectors. Additionally, it is found that the encapsulation of the GaSe photodetectors with hexagonal boron nitride (h-BN) can protect the GaSe from degradation and can help to achieve long-term stability of the devices.
“…This process can introduce strain in the atomic lattice thus modifying the optical and electronic properties of GaSe. [9g,20] A second observation is that the number of bubbles increases in time as shown by the bottom panel of Figure d. The initial formation and growth of an individual bubble is shown in Figure e by the cross section of the AFM images taken in the region highlighted by the arrows in panel (c).…”
Section: Resultsmentioning
confidence: 87%
“…Moreover, the presence of these materials can perturb the GaSe lattice and introduce strain, which may change the photoresponse. [9g,20]…”
Gallium selenide (GaSe) is a novel 2D material, which belongs to the layered III-VIA semiconductors family and attracted interest recently as it displays single-photon emitters at room temperature and strong optical nonlinearity. Nonetheless, few-layer GaSe is not stable under ambient conditions and it tends to degrade over time. Here atomic force microscopy, Raman spectroscopy, and optoelectronic measurements are combined in photodetectors based on thin GaSe to study its long-term stability. It is found that the GaSe flakes exposed to air tend to decompose forming first amorphous selenium and Ga 2 Se 3 and subsequently Ga 2 O 3 . While the first stage is accompanied by an increase in photocurrent, in the second stage, a decrease in photocurrent is observed, which leads to the final failure of GaSe photodetectors. Additionally, it is found that the encapsulation of the GaSe photodetectors with hexagonal boron nitride (h-BN) can protect the GaSe from degradation and can help to achieve long-term stability of the devices.
“…Moreover, lattice vacancies and atomic-level defect combined with the presence of light can accelerate the oxidation process [4][5][6][7][8], which is typically accompanied by a degradation of the electrical and optical properties reducing the device performance [9][10]. Furthermore, shining high intensity light on 2D materials can induce additional processes of photo-oxidation [11][12][13][14]. The overall performance reduction induced by oxidation seems to be one of the main issues to solve in developing industrial applications based on 2D materials, therefore controlling the oxidation process is a very active subject for both fundamental and applied research in the context of band engineering.…”
In two-dimensional materials research, oxidation is usually considered as a common source for the degradation of electronic and optoelectronic devices or even device failure. However, in some cases a controlled oxidation can open the possibility to widely tune the band structure of 2D materials. In particular, we demonstrate the controlled oxidation of titanium trisulfide (TiS3), a layered semiconductor that has attracted much attention recently thanks to its quasi-1D electronic and optoelectronic properties and its direct bandgap of 1.1 eV. Heating TiS3 in air above 300 °C gradually converts it into TiO2, a semiconductor with a wide bandgap of 3.2 eV with applications in photo-electrochemistry and catalysis. In this work, we investigate the controlled thermal oxidation of individual TiS3 nanoribbons and its influence on the optoelectronic properties of TiS3-based photodetectors. We observe a step-wise change in the cut-off wavelength from its pristine value ~1000 nm to 450 nm after subjecting the TiS3 devices to subsequent thermal treatment cycles. Ab-initio and many-body calculations confirm an increase in the bandgap of titanium oxysulfide (TiO2-xSx) when increasing the amount of oxygen and reducing the amount of sulfur.
“…However, ReS 2 within ten layers are all considered to have a direct bandgap [11], which means ReS 2 within ten layers can all perform well. Besides, the asymmetric lattice structure leads to weaker interlayer coupling energy, which benefits the exfoliation work, and thus makes the synaptic device much easier to fabricate [12][13][14][15]. In this study, ReS 2 film is used as a channel material.…”
Synaptic devices are necessary to meet the growing demand for the smarter and more efficient system. In this work, the anisotropic rhenium disulfide (ReS 2) is used as a channel material to construct a synaptic device and successfully emulate the long-term potentiation/depression behavior. To demonstrate that our device can be used in a large-scale neural network system, 165 pictures from Yale Face database are selected for evaluation, of which 120 pictures are used for artificial neural network (ANN) training, and the remaining 45 pictures are used for ANN testing. A three-layer ANN containing more than 10 5 weights is proposed for the face recognition task. Also 120 continuous modulated conductance states are selected to replace weights in our well-trained ANN. The results show that an excellent recognition rate of 100% is achieved with only 120 conductance states, which proves a high potential of our device in the artificial neural network field.
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