Size quantization effects in cadmium sulfide layers formed by a Langmuir-Blodgett technique

Smotkin, Eugene S.; Lee, Chongmok; Bard, Allen J.; Campion, Alan; Fox, Marye Anne; Mallouk, Thomas E.; Webber, S. E.; White, J. M.

doi:10.1016/0009-2614(88)87365-2

Cited by 189 publications

(78 citation statements)

References 19 publications

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“…This trend is very similar to that observed on samples not treated with H2S, enabling us to think that, in these cases, no particle is formed on the very tip of the stylus. This fact is not surprising as the particle formation process is an intrinsically random one (21,23); i.e., it is impossible to control and predict the exact position of the synthesized clusters inside the organic matrix. From this viewpoint, 60% of working junctions can be considered a good yield.…”

Section: Methodsmentioning

confidence: 99%

Room-temperature single-electron junction.

Facci¹,

Erokhin²,

Carrara³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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The design, realization, and test performances of an electronic junction based on single-electron phenomena that works in the air at room temperature are hereby reported. The element consists of an electrochemically etched sharp tungsten stylus over whose tip a nanometer-size crystal was synthesized. Langmuir-Blodgett films of cadmium arachidate were transferred onto the stylus and exposed to a H2S atmosphere to yield CdS nanocrystals (30-50 A in diameter) imbedded into an organic matrix. The stylus, biased with respect to a flat electrode, was brought to the tunnel distance from the film and a constant gap value was maintained by a piezo-electric actuator driven by a feedback circuit fed by the tunneling current. With this set-up, it is possible to measure the behavior of the current flowing through the quantum dot when a bias voltage is applied. Voltage-current characteristics measured in the system displayed singleelectron trends such as a Coulomb blockade and Coulomb staircase and revealed capacitance values as small as 10-19 F.For several years, single-electron phenomena have attracted the interest of researchers from basic and applied viewpoints (1-5). These kinds of phenomena can take place when a small conductive particle is placed between two electrodes and is spaced asymmetrically from them by two tunneling gaps. In this case, a quantized charging of the particle resulting in the quantized increase of the current that flows through the system when a bias voltage is applied is observed. The conditions for achieving such a situation imply that the capacitance C of the structure is small enough to make the charging energy of the junction (e2/2C) exceed the thermal energy kT. Namely, roomtemperature monoelectron junctions typically require particles not larger than several nanometers in diameter (quantum dots) (6-9).The possibility of controlling the signal at the level of a single electron will allow the realization of a new class of devices (3)(4)(5)10). These new electronic junction can be foreseen to display very low energy consumption, an ultra-high scale of integration, and fast commutation time.The increasing interest in monoelectron phenomena has stimulated researchers to develop techniques for forming suitable junctions. The main efforts have focused upon the minimization of the element sizes by exploiting lithography processes. Striking results have been recently achieved in this field (11-13). As an alternative to this approach, techniques for nanoparticle formation, localization, and contacting with scanning tunneling microscope (STM) tip have been developed. Consequently, low (14-18) and room (6, 7) temperature monoelectron phenomena have been reported on nanoclusters of various natures and have been synthesized by different methods involving physical and chemical approaches. Among the different methods for producing these granules, one of the most promising seems to be that based on the synthesis of nanometer-size semiconducting granules from LangmuirBlodgett (LB) film precursors (7)....

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Section: Methodsmentioning

confidence: 99%

Room-temperature single-electron junction.

Facci¹,

Erokhin²,

Carrara³

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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“…Although a variety of routes are presently being used to develop these nanocomposites, Langmuir-Blodgett (LB) and self assembly (SA) processes are important owing essentially to their versatility to produce organized layered structures of a large variety of molecule/supermolecules with suitably designed architecture and functionality [9]. In particular, LB multilayers have been used to grow chalcogenide semiconducting nanoclusters in organic fatty acid matrix through post deposition treatment [10][11][12][13]. The interest in this approach is primarily because of the high degree of molecular order present in LB multilayers, which is expected to assist in achieving better control over the geometry, size and distribution of the nanoclusters.…”

Section: Introductionmentioning

confidence: 99%

Molecular packing in CdS containing conducting polymer composite LB multilayers

Vidya¹,

Kumar²,

Narang³

et al. 2002

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Langmuir-Blodgett (LB) technique has been used to deposit composite multilayers of poly (3-octylthiophene)-cadmium arachidate (POT-CdA) and polyaniline-cadmium arachidate (PANI-CdA). These were used as precursors to develop semiconducting CdS nanoclusters within the conducting polymer based multilayers. The presence of CdS in the multilayers was determined by Fourier transform infrared spectroscopy (FTIR), UV -Vis and Raman spectroscopy. The structural changes occurring as a consequence of CdS formation have been characterized using X-ray reflection and grazing incidence X-ray diffraction (GIXD) techniques. As-deposited POT-CdA multilayers exhibit good vertical as well as in-plane structure similar to that of CdA. In contrast, PANI-CdA multilayers have poor structural order. The in-plane molecular packing in CdA and PANI-CdA multilayers after H 2 S exposure has mixed domains of rectangular (herringbone) and hexagonal arrangements. In the case of POT-CdA multilayers, however, the original rectangular packing is retained.

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“…[10][11][12][13][14] A similar idea has been exploited in our previous publications [15][16][17] to form CdS nanoparticles within calixarene LB films. It was suggested there that the presence of calixarene cavities restricts segregation of CdS, and much smaller CdS particles were formed as a result.…”

Section: Introductionmentioning

confidence: 91%

Electron beam stimulated formation of CdS nanoparticles within calixarene Langmuir–Blodgett films

Nabok

Ray

Hassan

2000

Journal of Applied Physics

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Two possible types of cadmium sulphide ͑CdS͒ nanostructures can be formed within LangmuirBlodgett ͑LB͒ films of calixarene Cd salt as a result of exposure to H 2 S gas: nanoclusters with the size of about 1.5 nm or two-dimensional planes with the thickness of about 1.7 nm. Transmission electron microscopy and electron diffraction studies on calixarene/CdS LB films show that CdS particles are not present in the fresh samples at the beginning, but they are gradually formed under exposure to a high energy electron beam. A blueshift of the first exciton absorption band and an increase of the extinction coefficient, caused by exposure to H 2 S gas, were found with UV-visible optical spectroscopy and surface plasmon resonance, respectively.

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Size quantization effects in cadmium sulfide layers formed by a Langmuir-Blodgett technique

Cited by 189 publications

References 19 publications

Room-temperature single-electron junction.

Room-temperature single-electron junction.

Molecular packing in CdS containing conducting polymer composite LB multilayers

Electron beam stimulated formation of CdS nanoparticles within calixarene Langmuir–Blodgett films

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