N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the p...N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the polycrystalline nature of the deposited films.The crystalline structure is influenced by the variation of OPP.Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square(RMS)roughness when the OPP is increased above 1.4×10-3 Pa.X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP,noticeably N 1s XPS peaks are hardly identified at 9.5×10-3 Pa.The average visible transmittance(380-700 nm) is increased with the increase of OPP(from～17%to 70%),and the optical absorption edge shifts towards the shorter wavelength.The films deposited with low OPP(≤3.0×10-4 Pa)show n-type conductivity and those deposited with high OPP(≥9.0×10-4 Pa)are highly resistive(>105Ω·cm)展开更多
Insightful knowledge on quantum nanostructured materials is paramount to engineer and exploit their vast gamut of applications.Here,a formalism based on the single-band effective mass equation was developed to determi...Insightful knowledge on quantum nanostructured materials is paramount to engineer and exploit their vast gamut of applications.Here,a formalism based on the single-band effective mass equation was developed to determine the light absorption of colloidal quantum dots(CQDs)embedded in a wider bandgap semiconductor host,employing only three parameters(dots/host potential barrier,effective mass,and QD size).It was ascertained how to tune such parameters to design the energy level structure and consequent optical response.Our findings show that the CQD size has the biggest effect on the number and energy of the confined levels,while the potential barrier causes a linear shift of their values.While smaller QDs allow wider energetic separation between levels(as desired for most quantumbased technologies),the larger dots with higher number of levels are those that exhibit the strongest absorption.Nevertheless,it was unprecedently shown that such quantum-enabled absorption coefficients can reach the levels(10^(4)–10^(5) cm^(−1))of bulk semiconductors.展开更多
基金the Portuguese Ministry of Science and Technology(FCT-MCTES)for offering post-doctoral fellowships through the grants SFRH/BPD/34542/2007 and SFRH/BPD/35055/2007,respectivelyfinanced by FCT-MCTES through CENIMAT-I3N
文摘N-doped ZnO films were radio frequency(RF)sputtered on glass substrates and studied as a function of oxygen partial pressure(OPP)ranging from 3.0×10-4 to 9.5×10-3 Pa.X-ray diffraction patters confirmed the polycrystalline nature of the deposited films.The crystalline structure is influenced by the variation of OPP.Atomic force microscopy analysis confirmed the agglomeration of the neighboring spherical grains with a sharp increase of root mean square(RMS)roughness when the OPP is increased above 1.4×10-3 Pa.X-ray photoelectron spectroscopy analysis revealed that the incorporation of N content into the film is decreased with the increase of OPP,noticeably N 1s XPS peaks are hardly identified at 9.5×10-3 Pa.The average visible transmittance(380-700 nm) is increased with the increase of OPP(from～17%to 70%),and the optical absorption edge shifts towards the shorter wavelength.The films deposited with low OPP(≤3.0×10-4 Pa)show n-type conductivity and those deposited with high OPP(≥9.0×10-4 Pa)are highly resistive(>105Ω·cm)
基金This work was funded by FCT(Fundação para a Ciência e Tecnologia,I.P.)under the projects UIDB/50025/2020SuperSolar(PTDC/NAN-OPT/28430/2017)+2 种基金TACIT(PTCD/NAN-OPT/28837/2017)M.Alexandre also acknowledges funding by FCT,I.P.through the grant SFRH/BD/148078/2019We also acknowledge the support of SYNERGY,H2020-WIDESPREAD-2020-5,CSA,proposal n°952169.
文摘Insightful knowledge on quantum nanostructured materials is paramount to engineer and exploit their vast gamut of applications.Here,a formalism based on the single-band effective mass equation was developed to determine the light absorption of colloidal quantum dots(CQDs)embedded in a wider bandgap semiconductor host,employing only three parameters(dots/host potential barrier,effective mass,and QD size).It was ascertained how to tune such parameters to design the energy level structure and consequent optical response.Our findings show that the CQD size has the biggest effect on the number and energy of the confined levels,while the potential barrier causes a linear shift of their values.While smaller QDs allow wider energetic separation between levels(as desired for most quantumbased technologies),the larger dots with higher number of levels are those that exhibit the strongest absorption.Nevertheless,it was unprecedently shown that such quantum-enabled absorption coefficients can reach the levels(10^(4)–10^(5) cm^(−1))of bulk semiconductors.
