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Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors.

Mahjouri-Samani M, Lin MW, Wang K, Lupini AR, Lee J, Basile L, Boulesbaa A, Rouleau CM, Puretzky AA, Ivanov IN, Xiao K, Yoon M, Geohegan DB - Nat Commun (2015)

Bottom Line: The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics.Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns.This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

View Article: PubMed Central - PubMed

Affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

ABSTRACT
The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional crystalline semiconductors as building blocks in next-generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate an approach for the formation of lithographically patterned arrays of lateral semiconducting heterojunctions within a single two-dimensional crystal. Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are studied by Raman and photoluminescence spectroscopy, atomically resolved scanning transmission electron microscopy and device characterization. This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

No MeSH data available.


Conversion of MoSe2 to MoS2 and the formation of lateral heterojunction arrays.(a,b) Optical and atomic force microscopy images of a typical MoSe2 monolayer with a lateral size of ∼40 μm. (c,d) Raman maps of a monolayer nanosheet before and after the complete conversion process (400 pulses at 700 °C), respectively, indicating uniform intensity across the entire crystal. (e,f) Representative Raman and PL spectra of the pristine MoSe2 and converted MoS2 regions. (g,h) Various examples of lateral heterojunction arrays formed within monolayer crystals by patterning and selective conversion processes. The green, red and combined Raman maps are obtained from corresponding optical images, representing the MoS2 (intensity map at 403 cm−1), MoSe2 (intensity map at 238 cm−1) and overlaid MoSe2/MoS2 regions, respectively. Scale bars, 5 μm.
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f2: Conversion of MoSe2 to MoS2 and the formation of lateral heterojunction arrays.(a,b) Optical and atomic force microscopy images of a typical MoSe2 monolayer with a lateral size of ∼40 μm. (c,d) Raman maps of a monolayer nanosheet before and after the complete conversion process (400 pulses at 700 °C), respectively, indicating uniform intensity across the entire crystal. (e,f) Representative Raman and PL spectra of the pristine MoSe2 and converted MoS2 regions. (g,h) Various examples of lateral heterojunction arrays formed within monolayer crystals by patterning and selective conversion processes. The green, red and combined Raman maps are obtained from corresponding optical images, representing the MoS2 (intensity map at 403 cm−1), MoSe2 (intensity map at 238 cm−1) and overlaid MoSe2/MoS2 regions, respectively. Scale bars, 5 μm.

Mentions: Raman and PL spectroscopy were used to probe the structures spatially, monitor the conversion degree and to map the heterojunction arrays within the monolayer crystals. Figure 2a,b shows optical and atomic force microscopy images of a typical MoSe2 2D crystal. The corresponding Raman maps of the crystal before and after the full conversion process are shown in Fig. 2c,d. The MoSe2 and MoS2 Raman maps are plotted for the E12g mode of MoSe2 at 238 cm−1 and E12g modes of MoS2 at 403 cm−1, respectively1013. Representative Raman and PL spectra of the flake before and after the conversion process are shown in Fig. 2e,f, indicating MoSe2 and MoS2 Raman peaks similar to those reported in the literature1013. The uniform intensity distribution in the Raman maps indicates spatial uniformity of the 2D crystals both before and after the conversion. Figure 2g,h shows the formation of various lateral heterojunction arrays prepared by our patterning and selective conversion process. Similarly, the uniform intensity of Raman maps clearly indicates the spatial uniformity of the MoSe2 and MoS2 domains, and formation of heterojunction arrays within the monolayer crystals. The Raman and PL spectra obtained from the pristine and converted regions of the crystals are similar to the ones shown in Fig. 2e,f.


Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors.

Mahjouri-Samani M, Lin MW, Wang K, Lupini AR, Lee J, Basile L, Boulesbaa A, Rouleau CM, Puretzky AA, Ivanov IN, Xiao K, Yoon M, Geohegan DB - Nat Commun (2015)

Conversion of MoSe2 to MoS2 and the formation of lateral heterojunction arrays.(a,b) Optical and atomic force microscopy images of a typical MoSe2 monolayer with a lateral size of ∼40 μm. (c,d) Raman maps of a monolayer nanosheet before and after the complete conversion process (400 pulses at 700 °C), respectively, indicating uniform intensity across the entire crystal. (e,f) Representative Raman and PL spectra of the pristine MoSe2 and converted MoS2 regions. (g,h) Various examples of lateral heterojunction arrays formed within monolayer crystals by patterning and selective conversion processes. The green, red and combined Raman maps are obtained from corresponding optical images, representing the MoS2 (intensity map at 403 cm−1), MoSe2 (intensity map at 238 cm−1) and overlaid MoSe2/MoS2 regions, respectively. Scale bars, 5 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525195&req=5

f2: Conversion of MoSe2 to MoS2 and the formation of lateral heterojunction arrays.(a,b) Optical and atomic force microscopy images of a typical MoSe2 monolayer with a lateral size of ∼40 μm. (c,d) Raman maps of a monolayer nanosheet before and after the complete conversion process (400 pulses at 700 °C), respectively, indicating uniform intensity across the entire crystal. (e,f) Representative Raman and PL spectra of the pristine MoSe2 and converted MoS2 regions. (g,h) Various examples of lateral heterojunction arrays formed within monolayer crystals by patterning and selective conversion processes. The green, red and combined Raman maps are obtained from corresponding optical images, representing the MoS2 (intensity map at 403 cm−1), MoSe2 (intensity map at 238 cm−1) and overlaid MoSe2/MoS2 regions, respectively. Scale bars, 5 μm.
Mentions: Raman and PL spectroscopy were used to probe the structures spatially, monitor the conversion degree and to map the heterojunction arrays within the monolayer crystals. Figure 2a,b shows optical and atomic force microscopy images of a typical MoSe2 2D crystal. The corresponding Raman maps of the crystal before and after the full conversion process are shown in Fig. 2c,d. The MoSe2 and MoS2 Raman maps are plotted for the E12g mode of MoSe2 at 238 cm−1 and E12g modes of MoS2 at 403 cm−1, respectively1013. Representative Raman and PL spectra of the flake before and after the conversion process are shown in Fig. 2e,f, indicating MoSe2 and MoS2 Raman peaks similar to those reported in the literature1013. The uniform intensity distribution in the Raman maps indicates spatial uniformity of the 2D crystals both before and after the conversion. Figure 2g,h shows the formation of various lateral heterojunction arrays prepared by our patterning and selective conversion process. Similarly, the uniform intensity of Raman maps clearly indicates the spatial uniformity of the MoSe2 and MoS2 domains, and formation of heterojunction arrays within the monolayer crystals. The Raman and PL spectra obtained from the pristine and converted regions of the crystals are similar to the ones shown in Fig. 2e,f.

Bottom Line: The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics.Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns.This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

View Article: PubMed Central - PubMed

Affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

ABSTRACT
The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional crystalline semiconductors as building blocks in next-generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate an approach for the formation of lithographically patterned arrays of lateral semiconducting heterojunctions within a single two-dimensional crystal. Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are studied by Raman and photoluminescence spectroscopy, atomically resolved scanning transmission electron microscopy and device characterization. This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

No MeSH data available.