12 research outputs found
Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS<sub>2</sub>/GaAs
The new generation of two-dimensional (2D) materials has shown a broad range
of applications for optical and electronic devices. Understanding the
properties of these materials when integrated with the more traditional
three-dimensional (3D) semiconductors is an important challenge for the
implementation of ultra-thin electronic devices. Recent observations have shown
that by combining MoS with GaAs it is possible to develop high quality
photodetectors and solar cells. Here, we present a study of the effects of
intrinsic GaAs, p-doped GaAs, and n-doped GaAs substrates on the
photoluminescence of monolayer MoS. We observe a decrease of an order of
magnitude in the emission intensity of MoS in all MoS/GaAs
heterojunctions, when compared to a control sample consisting of a MoS
monolayer isolated from GaAs by a few layers of hexagonal boron nitride. We
also see a dependence of the trion to A-exciton emission ratio in the
photoluminescence spectra on the type of substrate, a dependence that we relate
to the static charge exchange between MoS and the substrates when the
junction is formed. Scanning Kelvin probe microscopy measurements of the
heterojunctions suggest type-I band alignments, so that excitons generated on
the MoS monolayer will be transferred to the GaAs substrate. Our results
shed light on the charge exchange leading to band offsets in 2D/3D
heterojunctions which play a central role in the understanding and further
improvement of electronic devices.Comment: Accepted in Applied Physics Letter
Atributos físico-hídricos de um latossolo de cerrado em diferentes posições de amostragem na lavoura cafeeira
Association between insulin-like growth factor I (IGF-I) microsatellite polymorphisms and important economic traits in pigs
Occurrence of Toxoplasma gondii and risk factors for infection in pigs raised and slaughtered in the Triângulo Mineiro region, Minas Gerais, Brazil
Brazilian Flora 2020: Leveraging the power of a collaborative scientific network
International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora