Inside a nanocrystal-based photodiode using photoemission microscopy

Cavallo, Mariarosa; alchaar, rodolphe; bossavit, erwan; zhang, huichen; Dang, Tung Huu; Khalili, Adrien; Prado, Yoann; Utterback, James M.; Ithurria, Sandrine; Dudin, Pavel; Ávila, J.; pierucci, debora; Lhuillier, Emmanuel

doi:10.1039/d3nr00999h

Cited by 6 publications

(6 citation statements)

References 46 publications

(57 reference statements)

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“…As a result, it was not well-suited for conventional vertical geometry diodes, which led us to focus on a planar version of the junction. 39 The fabrication procedure for the planar junction is outlined in Figure S27. Briefly, a Si/SiO 2 wafer was initially covered with a gold layer to minimize sample charging.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Second, the method, relying on soft X-rays, had a very limited photoelectron escape depth (few nm), which meant that it could only probe the sample’s surface. As a result, it was not well-suited for conventional vertical geometry diodes, which led us to focus on a planar version of the junction . The fabrication procedure for the planar junction is outlined in Figure S27.…”

Section: Resultsmentioning

confidence: 99%

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Photoemission Insight on Narrow Band Gap PbS Quantum Dots Relevant for Infrared Imaging

Zhang,

Ledos,

Cavallo

et al. 2024

J. Phys. Chem. C

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In recent years, the interest for narrow band gap colloidal quantum dots (CQDs) has shifted from materials optimized for solar cells (with E G ≈ 1.2 eV) to materials with properties at longer wavelengths. This shift necessitates a systematic investigation of their electronic properties to optimize photodiode designs effectively. In this study, we utilized X-ray photoemission to systematically determine how the band gap (with absorption maximum wavelengths of 1000, 1200, 1400, and 1550 nm) and surface chemistry (short halides and thiols) influence the band alignment and the core levels in PbS nanocrystals. Our research provides evidence for a shift from a quasi-intrinsic behavior for the narrowest band gap to an exclusively n-type nature for the particles with the largest size, potentially indicating the emergence of degenerate doping. Core-level analysis reveals that the effect of ligands extends beyond dipole behavior, also inducing charge transfer leading to the formation of metallic islands, which might be detrimental to photodetection. Furthermore, by employing scanning photoemission microscopy, we gained direct access to the photodiode's built-in potential, a parameter typically obtained through indirect modeling. We then discussed how the particle size influences this property. This study lays the foundation for a more rational design of PbS CQD-based photodiodes operating in the short-wave infrared spectrum.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Photoemission Insight on Narrow Band Gap PbS Quantum Dots Relevant for Infrared Imaging

Zhang,

Ledos,

Cavallo

et al. 2024

J. Phys. Chem. C

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“…Recently, Cavallo et al have reported the use of such a method to probe the scalar energy landscape of NC-based field-effect transistors 20,21 and a photodiode. 22 In particular, the method has been insightful in probing surface band bending at the NC semiconductor−electrode interface 20 by providing direct evidence of the gate bias effect on the band alignment and unveiling the built-in potential of a diode. 22 In this report, we explore how photoemission microscopy can be used to probe the vectorial electric field distribution in a FPA-like structure under operation.…”

Section: ■ Introductionmentioning

confidence: 99%

“…22 In particular, the method has been insightful in probing surface band bending at the NC semiconductor−electrode interface 20 by providing direct evidence of the gate bias effect on the band alignment and unveiling the built-in potential of a diode. 22 In this report, we explore how photoemission microscopy can be used to probe the vectorial electric field distribution in a FPA-like structure under operation. Such output will be critical for the future modeling of complex devices such as infrared imagers.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Here, we explore the use of photoemission microscopy as a tool to unveil in operando the electronic properties of the FPA. Recently, Cavallo et al have reported the use of such a method to probe the scalar energy landscape of NC-based field-effect transistors , and a photodiode . In particular, the method has been insightful in probing surface band bending at the NC semiconductor–electrode interface by providing direct evidence of the gate bias effect on the band alignment and unveiling the built-in potential of a diode .…”

Section: Introductionmentioning

confidence: 99%

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In Situ Mapping of the Vectorial Electric Field within a Nanocrystal-Based Focal Plane Array Using Photoemission Microscopy

Khalili

Cavallo

Bossavit

et al. 2023

ACS Appl. Electron. Mater.

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Within a few years, nanocrystal-based infrared devices have achieved significant progress and advancements, including high-quality imaging systems. This raises the need to develop tools that can probe the active material of the device in situ and in operando to gain a deeper understanding of their operation beyond the overall response of the device. Here, we investigate a short-wave infrared imager based on HgTe nanocrystals with photoconductive operation, which now proposes imaging at wavelengths beyond the traditional InGaAs technology. We demonstrate that we can use photoemission microscopy to probe the energy landscape of this imaging array. Finally, we further use the high spatial resolution of the method to get access to the vectorial distribution of the electric field.

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The Rise of HgTe Colloidal Quantum Dots for Infrared Optoelectronics

Sergeeva,

Zhang,

Portniagin

et al. 2024

Adv Funct Materials

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Among materials produced as colloidal quantum dots (CQDs), HgTe has a special status being the only material covering the whole infrared range from the visible to the THz (0.7–100 µm). This unique property resulting from its electronic structure, combined with an air stability and a capacity for charge conduction has generated consistent and massive efforts to produce and improve HgTe CQDs over the past two decades. Meanwhile, HgTe CQDs offer an infrared platform more advanced than any other colloidal alternatives in the mid‐wave infrared regarding their integration into advanced photonic and optoelectronic applications. Here, the latest developments of HgTe CQDs relative to the material's growth, electron structure modelling, its integration into photonic structures and its transfer as the active material from single element devices toward complex sensors and infrared imagers are reviewed. Finally, a discussion about the potential of this material for industry, rising new challenges beyond economical and production considerations at low technological readiness level, relative to the material and device design, is also included.

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Inside a nanocrystal-based photodiode using photoemission microscopy

Abstract: As nanocrystal-based devices gain maturity, a comprehensive understanding of their electronic structure is necessary for further optimization. Most spectroscopic techniques typically examine pristine materials and disregard the coupling of the...

Cited by 6 publications

References 46 publications

Photoemission Insight on Narrow Band Gap PbS Quantum Dots Relevant for Infrared Imaging

Photoemission Insight on Narrow Band Gap PbS Quantum Dots Relevant for Infrared Imaging

In Situ Mapping of the Vectorial Electric Field within a Nanocrystal-Based Focal Plane Array Using Photoemission Microscopy

The Rise of HgTe Colloidal Quantum Dots for Infrared Optoelectronics

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