Elena V. Rogojina

Bio: Elena V. Rogojina is an academic researcher from DuPont. The author has contributed to research in topics: Silicon & Substrate (electronics). The author has an hindex of 13, co-authored 29 publications receiving 1105 citations.

Silicon nanocrystals with ensemble quantum yields exceeding 60

Abstract: Silicon nanocrystals with diameters of less than 5nm show efficient photoluminescence at room temperature. For ensembles of silicon quantum dots, previous reports of photoluminescence quantum yields have usually been in the few percent range, and generally less than 30%. Here we report the plasma synthesis of silicon quantum dots and their subsequent wet-chemical surface passivation with organic ligands under strict exclusion of oxygen. Photoluminescence quantum yields exceeding 60% have been achieved at peak wavelengths of about 789nm.

In situ modification of group iv nanoparticles using gas phase nanoparticle reactors

Abstract: A method for creating an organically capped Group IV semiconductor nanoparticle is disclosed. The method includes flowing a Group IV semiconductor precursor gas into a chamber. The method also includes generating a set of Group IV semiconductor precursor radical species from the Group IV semiconductor precursor gas with a laser pyrolysis apparatus, wherein the set of the Group IV semiconductor precursor radical species nucleate to form the Group IV semiconductor nanoparticle; and flowing an organic capping agent precursor gas into the chamber. The method further includes generating a set of organic capping agent radical species from the organic capping agent precursor gas, wherein the set of organic capping agent radical species reacts with a surface of the Group IV semiconductor nanoparticle and forms the organically capped Group IV semiconductor nanoparticle.

Methods of filling a set of interstitial spaces of a nanoparticle thin film with a dielectric material

Abstract: A method of forming a densified nanoparticle thin film is disclosed. The method includes positioning a substrate in a first chamber; and depositing a nanoparticle ink, the nanoparticle ink including a set of Group IV semiconductor particles and a solvent. The method also includes heating the nanoparticle ink to a first temperature between about 30°C and about 300°C, and for a first time period between about 1 minute and about 60 minutes, wherein the solvent is substantially removed, and a porous compact is formed; and positioning the substrate in a second chamber, the second chamber having a pressure of between about 1 x 10-7 Torr and about 1 x 10-4 Torr. The method further includes depositing on the porous compact a dielectric material; wherein the densified nanoparticle thin film is formed.

Plasma synthesis and liquid-phase surface passivation of brightly luminescent Si nanocrystals

Abstract: While silicon's optical properties are improved at the nanoscale, they also become highly sensitive to the properties of the surfaces and interfaces of silicon nanostructures. For instance, while reported quantum yields for photoluminescence of silicon quantum dots covered by a native oxide are often in the few percent range, quantum yields as high as 30% have been found in quantum dots whose surfaces were passivated by covalently bonded organic molecules. In this paper, we describe an approach that is based on the gas phase synthesis of silicon quantum dots in a nonthermal plasma, and the subsequent organic surface passivation in the liquid phase. Nanocrystals are formed within a few milliseconds with a high mass yield in a nonthermal plasma. Various organic ligands such as octadecene, dodecence, and styrene are grafted onto the nanocrystal surfaces in a reaction known as hydrosilylation. Materials are characterized through transmission electron microscopy, atomic force microscopy, and fluorescence measurements. The particle size distributions are found to be relatively monodisperse and are well controllable through the plasma process parameters. Photoluminescence quantum yields as high as 60–70% have been achieved for particles luminescing in the red range of the visible spectrum.

Methods for creating a densified group iv semiconductor nanoparticle thin film

Abstract: A method of forming a densified nanoparticle thin film in a chamber is disclosed. The method includes positioning a substrate in the chamber; and depositing a nanoparticle ink, the nanoparticle ink including a set of Group IV semiconductor particles and a solvent. The method also includes heating the nanoparticle ink to a first temperature between about 30°C and about 300°C, and for a first time period between about 1 minute and about 60 minutes, wherein the solvent is substantially removed, and a porous compact is formed. The method further includes exposing the porous compact to an HF vapor for a second time period of between about 2 minutes and about 20 minutes, and heating the porous compact for a second temperature of between about 25°C and about 60° C; and heating the porous compact to a third temperature between about 100° C and about 1000° C, and for a third time period of between about 5 minutes and about 10 hours; wherein the densified nanoparticle thin film is formed.

Emergence of colloidal quantum-dot light-emitting technologies

Abstract: This Review article summarizes the key advantages of using quantum dots (QDs) as luminophores in light-emitting devices (LEDs) and outlines the operating mechanisms of four types of QD-LED. The key scientific and technological challenges facing QD-LED commercialization are identified, together with on-going strategies to overcome these challenges.

Semiconductor device, and manufacturing method thereof

Abstract: An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor quantum dots and quantum dot arrays and applications of multiple exciton generation to third-generation photovoltaic solar cells.

Abstract: Here, we will first briefly summarize the general principles of QD synthesis using our previous work on InP as an example. Then we will focus on QDs of the IV-VI Pb chalcogenides (PbSe, PbS, and PbTe) and Si QDs because these were among the first QDs that were reported to produce multiple excitons upon absorbing single photons of appropriate energy (a process we call multiple exciton generation (MEG)). We note that in addition to Si and the Pb-VI QDs, two other semiconductor systems (III-V InP QDs(56) and II-VI core-shell CdTe/CdSe QDs(57)) were very recently reported to also produce MEG. Then we will discuss photogenerated carrier dynamics in QDs, including the issues and controversies related to the cooling of hot carriers and the magnitude and significance of MEG in QDs. Finally, we will discuss applications of QDs and QD arrays in novel quantum dot PV cells, where multiple exciton generation from single photons could yield significantly higher PV conversion efficiencies.

Prospects of Nanoscience with Nanocrystals

Abstract: Colloidal nanocrystals (NCs, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from medicine to electronic and optoelectronic devices. Today’s strong research focus on NCs has been prompted by the tremendous progress in their synthesis. Impressively narrow size distributions of just a few percent, rational shape-engineering, compositional modulation, electronic doping, and tailored surface chemistries are now feasible for a broad range of inorganic compounds. The performance of inorganic NC-based photovoltaic and light-emitting devices has become competitive to other state-of-the-art materials. Semiconductor NCs hold unique promise for near- and mid-infrared technologies, where very few semiconductor materials are available. On a purely fundamental side, new insights into NC growth, chemical transformations, and self-organization can be gained from rapidly progressing in situ characterization and direct imaging techniques. New phenom...

Silicon nanostructures for photonics and photovoltaics

Abstract: Silicon has long been established as the material of choice for the microelectronics industry. This is not yet true in photonics, where the limited degrees of freedom in material design combined with the indirect bandgap are a major constraint. Recent developments, especially those enabled by nanoscale engineering of the electronic and photonic properties, are starting to change the picture, and some silicon nanostructures now approach or even exceed the performance of equivalent direct-bandgap materials. Focusing on two application areas, namely communications and photovoltaics, we review recent progress in silicon nanocrystals, nanowires and photonic crystals as key examples of functional nanostructures. We assess the state of the art in each field and highlight the challenges that need to be overcome to make silicon a truly high-performing photonic material.