Structural and infrared absorption properties of self-organized InGaAs GaAs quantum dots multilayers

Self-organized InGaAs/GaAs quantum dots (QDs) stacked multilayers have been prepared by solid source molecular beam epitaxy. Cross-sectional transmission electron microscopy shows that the InGaAs QDs are nearly perfectly vertically aligned in the growth direction [100]. The filtering effect on the QDs distribution is found to be the dominant mechanism leading to vertical alignment and a highly uniform size distribution. Moreover, we observe a distinct infrared absorption from the sample in the range of 8.6-10.7 mu m. This indicates the potential of QDs multilayer structure for use as infrared photodetector

Structure-Function Correlation of the Human Central Retina

The impact of retinal pathology detected by high-resolution imaging on vision remains largely unexplored. Therefore, the aim of the study was to achieve high-resolution structure-function correlation of the human macula in vivo.To obtain high-resolution tomographic and topographic images of the macula spectral-domain optical coherence tomography (SD-OCT) and confocal scanning laser ophthalmoscopy (cSLO), respectively, were used. Functional mapping of the macula was obtained by using fundus-controlled microperimetry. Custom software allowed for co-registration of the fundus mapped microperimetry coordinates with both SD-OCT and cSLO datasets. The method was applied in a cross-sectional observational study of retinal diseases and in a clinical trial investigating the effectiveness of intravitreal ranibizumab in macular telangietasia type 2. There was a significant relationship between outer retinal thickness and retinal sensitivity (p<0.001) and neurodegeneration leaving less than about 50 µm of parafoveal outer retinal thickness completely abolished light sensitivity. In contrast, functional preservation was found if neurodegeneration spared the photoreceptors, but caused quite extensive disruption of the inner retina. Longitudinal data revealed that small lesions affecting the photoreceptor layer typically precede functional detection but later cause severe loss of light sensitivity. Ranibizumab was shown to be ineffective to prevent such functional loss in macular telangietasia type 2.Since there is a general need for efficient monitoring of the effectiveness of therapy in neurodegenerative diseases of the retina and since SD-OCT imaging is becoming more widely available, surrogate endpoints derived from such structure-function correlation may become highly relevant in future clinical trials

J. Vac. Sci. Technol. B

The solid-solid chemical reactions of phenols or ketones, such as beta-naphthol (1) or anthron (2), with FeCl3. 6H(2)O by ultraviolet irradiation give coupling dimeric products. The mechanisms are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) of 2 or (001) of 1 exhibits stumpy protrusions all over the surface from the contact edge of the crystals, respectively, whereas the long side face (010) of 2 gives volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given. (C) 1999 American Vacuum Society. [S0734-211X(99)07705-7].The solid-solid chemical reactions of phenols or ketones, such as beta-naphthol (1) or anthron (2), with FeCl3. 6H(2)O by ultraviolet irradiation give coupling dimeric products. The mechanisms are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) of 2 or (001) of 1 exhibits stumpy protrusions all over the surface from the contact edge of the crystals, respectively, whereas the long side face (010) of 2 gives volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given. (C) 1999 American Vacuum Society. [S0734-211X(99)07705-7]

J. Vac. Sci. Technol. B

Regular nanostructures are formed by chemical reaction of ammonia gas with crystalline substituted benzoic acid such as p-bromobenzoic (la), p-toluic (Ib), p-aminobenzoic (Ic), and p-nitrobenzoic acid (Id). Their size and shape are determined and depicted by atomic force microscopy (AFM). AFM reveals that the crystal main face (100) of la, (100) of Ib, (100) of Ic, and (001) of Id exhibits craters and volcanoes, craters and volcanoes, volcanoes, and volcanoes, respectively, whereas the long side face (100) of Id gives rise to craters and volcanoes. All the experimental results are correlated with the crystal structures. Molecular interpretations of the AFM features of la, Ib, Ic, and Id are given. (C) 2000 American Vacuum Society. [S0734-211X(00)03206-6].Regular nanostructures are formed by chemical reaction of ammonia gas with crystalline substituted benzoic acid such as p-bromobenzoic (la), p-toluic (Ib), p-aminobenzoic (Ic), and p-nitrobenzoic acid (Id). Their size and shape are determined and depicted by atomic force microscopy (AFM). AFM reveals that the crystal main face (100) of la, (100) of Ib, (100) of Ic, and (001) of Id exhibits craters and volcanoes, craters and volcanoes, volcanoes, and volcanoes, respectively, whereas the long side face (100) of Id gives rise to craters and volcanoes. All the experimental results are correlated with the crystal structures. Molecular interpretations of the AFM features of la, Ib, Ic, and Id are given. (C) 2000 American Vacuum Society. [S0734-211X(00)03206-6]

J. Vac. Sci. Technol. B

The formation of regular nanostructures by photopolymerization of three diolefin derivative crystals, P2VB, DSP, and p-CPAEt is investigated using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) and (010) of P2VB exhibit volcanoes, whereas (100) and (010) of DSP give floelike structures. The main face and long side face of p-CPAEt give rise to volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features of P2VB and DSP are given. (C) 1999 American Vacuum Society. [S0734-211X(99)03606-9].The formation of regular nanostructures by photopolymerization of three diolefin derivative crystals, P2VB, DSP, and p-CPAEt is investigated using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) and (010) of P2VB exhibit volcanoes, whereas (100) and (010) of DSP give floelike structures. The main face and long side face of p-CPAEt give rise to volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features of P2VB and DSP are given. (C) 1999 American Vacuum Society. [S0734-211X(99)03606-9]

J. Vac. Sci. Technol. B

The gas-solid chemical reactions of pure crystalline alcohol, such as triphenyl carbinol (1) and 1,1-dipbenylethanol-1 (3), with HCl gas and their mechanism are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the main crystal face (001) of 1 exhibits volcanoes, whereas the long side face (100) gives volcanoes and craters in turn. Both (010) and (100) of 3 exhibit islands. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given. (C) 2000 American Vacuum Society.The gas-solid chemical reactions of pure crystalline alcohol, such as triphenyl carbinol (1) and 1,1-dipbenylethanol-1 (3), with HCl gas and their mechanism are studied using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the main crystal face (001) of 1 exhibits volcanoes, whereas the long side face (100) gives volcanoes and craters in turn. Both (010) and (100) of 3 exhibit islands. All of those are guided by the crystal structure. Molecular interpretations of the AFM features are given. (C) 2000 American Vacuum Society

Appl. Phys. A-Mater. Sci. Process.

Nanostructures are formed by photodimerization of crystalline 4,4&#39;-dimethylbenzophenone (1) through intermolecular hydrogen abstraction and Baeyer-Villiger reaction of 1 with m-chloroperoxybenzoic acid (MCPBA) (5) in the solid state. Atomic force microscopy (AFM) reveals that the crystal face 001) of 1 during photodimerization exhibits volcanoes, whereas the same face (001) of 1 yields both craters and volcanoes all over the surface from the contact edge of the crystals during the Baeyer-Villiger reaction. All the experimental results are correlated with the bulk crystal structure. Molecular interpretation of the AFM features of 1 is given.Nanostructures are formed by photodimerization of crystalline 4,4'-dimethylbenzophenone (1) through intermolecular hydrogen abstraction and Baeyer-Villiger reaction of 1 with m-chloroperoxybenzoic acid (MCPBA) (5) in the solid state. Atomic force microscopy (AFM) reveals that the crystal face 001) of 1 during photodimerization exhibits volcanoes, whereas the same face (001) of 1 yields both craters and volcanoes all over the surface from the contact edge of the crystals during the Baeyer-Villiger reaction. All the experimental results are correlated with the bulk crystal structure. Molecular interpretation of the AFM features of 1 is given

Normally incident infrared absorption in vertically aligned InGaAs/GaAs quantum dot superlattice

30-period InGaAs/GaAs quantum dot superlattice was fabricated by MBE. Using cross sectional transmission electron microscopy, the InGaAs quantum dots were found to be perfectly vertically aligned in the growth direction (100). Under normally incident radiation, a distinct absorption in the 8.5 similar to 10.4 mu m range peaked at 9.9 mu m was observed. The normally incident infrared absorption in vertically aligned quantum dot superlattice in the 8 similar to 12 mu m range was realized for the first time. This result indicates the potential application of the quantum dot superlattice structure without grating as normally incident infrared detector focal plane arrays

Structural, optical and intraband absorption properties of vertically aligned In0.32Ga0.68As/GaAs quantum dots superlattices

The self-organization growth of In0.32Ga0.68As/GaAs quantum dots (QDs) superlattices is investigated by molecular beam epitaxy. It is found that high growth temperature and low growth rate are favorable for the formation of perfect vertically aligned QDs superlattices. The aspect ratio (height versus diameter) of QD increases from 0.16 to 0.23 with increase number of bi-layer. We propose that this shape change play a significant role to improve the uniformity of QDs superlattices. Features in the variable temperature photoluminescence characteristics indicate the high uniformity of the QDs. Strong infrared absorption in the 8-12 mum was observed. Our results suggest the promising applications of QDs in normal sensitive infrared photodetectors. (C) 2001 Elsevier Science B.V. All rights reserved