Search

Low-dimensional carbon materials occupy a relevant role in the field of nanotechnology. Herein, the authors report a study conducted by atomic force microscopy and Raman spectroscopy on the deposition of carbon dots onto graphene surfaces. The study aims at understanding if and how the morphology and the microstructure of chemical vapor deposited graphene on Si/SiO2 may change due to the interaction with the carbon dots. Potential alteration in the graphene's electrical properties might be detrimental for optoelectronic applications. The deposition of carbon dots dispersed in water and ethanol solvents are explored to investigate the effect of solvents with different fluidic properties. The obtained results indicate that the carbon dots do not alter the quality of graphene.

In this note we present some stylised facts about the Covid-19 epidemic in the UK using daily time-series data published by Public Health England and the UK Department of Health and Social Care. We model the data on confirmed new cases using standard count-data models estimated at the country and national levels using a fixed rolling window to capture changes in the model parameters over time. We then use the most recent estimated models to carry out a simple realtime forecasting exercise aimed at predicting the date when the number of confirmed new cases will be approximately zero.

This paper considers the heterogeneous microfoundations of agglomeration economies. It studies the co-location of industries to look for evidence of labor pooling, input sharing, and knowledge spillovers. The novel contribution of the paper is that it estimates single-industry models using a common empirical framework that exploits the cross-sectional variation in how one industry co-locates with the other industries in the economy. This unified approach yields evidence on the relative importance of the Marshallian microfoundations at the single-industry level, allowing for like-for-like cross-industry comparisons on the determinants of agglomeration. Using UK data, we estimate such microfoundations models for 97 manufacturing sectors, including the classic agglomeration cases of automobiles, computers, cutlery, and textiles. These four cases – as with all of the individual industry models we estimate – clearly show the importance of the Marshallian forces. However, they also highlight how the importance of these forces varies across industries – implying that extrapolation from cases should be viewed with caution. The paper concludes with an investigation of the pattern of heterogeneity. The degree of an industry’s clustering (localization), dynamism, incumbent firm size, and worker education are shown to contribute to the pattern of heterogeneous microfoundations.

We use the move of the seat of the German government from Bonn to Berlin in 1999 to test competing views about the impact of public employment on private sector activity in a local labor market. A relocated public sector job might create new jobs in an area as it increases demand for locally-produced goods and services, or crowd out existing jobs due to upward pressure on housing rents. Using employment data from a panel of a 50% sample of establishments across 190 Berlin postcodes, we apply a treatment intensity approach which takes the possibility of spillovers into account. Results indicate that the arrival of 100 public sector jobs into an area generates 55 additional jobs in the private sector. There is evidence of spillovers: relocations up to a distance of 1km from a postcode boundary increases employment in the private sector by 36 jobs. These effects are coming through job gains in the service sector, while manufacturing employment is not influenced by the relocation.

We use the move of the seat of the German government from Bonn to Berlin in 1999 to test competing views about the impact of public employment on private sector activity in a local labor market. Using employment data from a 50% sample of establishments across 190 Berlin postcodes, we apply a treatment intensity approach which takes the possibility of spillovers into account. Results indicate that the arrival of 100 public sector jobs into an area generates 55 additional jobs in the private sector. There is evidence of spillovers: relocations up to a distance of 1km from a postcode boundary increases employment in the private sector by 36 jobs. These effects are coming through job gains in the service sector, while manufacturing employment is not influenced by the relocation.

A series of boron-doped homoepitaxial diamond films grown by Microwave Plasma Enhanced Chemical Vapor Deposition at the University of Rome "Tor Vergata" have been investigated with Raman spectroscopy. As the boron content increases, we observed systematic modifications in the Raman spectra of single-crystal diamonds. A significant change in the lineshape of the first-order Raman peak as well as a wide and structured signal at lower wavenumbers appeared simultaneously in samples grown at higher boron content.

In this work, a Raman and photoluminescence (PL) study of synthetic diamond films grown by hot filament chemical vapor deposition (CVD) on WC-Co is presented. The changes in the Raman spectrum induced by the different pretreatments of the substrate and/or different growth parameters of the films are discussed. In particular, the spectra of the films grown at 740 °C substrate temperature, 36 mbar pressure and 1.7% methane content in the CH4-H2 gas mixture and after different substrate pretreatments show all the features commonly observed in nanocrystalline diamond films, overlapped with a large PL background. A significant level of compressive stress is qualitatively deduced by the shift of the diamond Raman peaks. The different pretreatments of the substrates seem to have no influence on the quality of the diamond films. On the contrary, in samples grown at 700 °C substrate temperature, 10 mbar pressure and 1% methane content in the CH4-H2 gas mixture, the contribution of the non-diamond carbon phases to the Raman spectrum substantially decreases, even though the diamond Raman peak remains shifted and broad. Impurities in the films have been identified by means of low-temperature PL measurements. W and Si-related optical centers have been clearly observed, together with a band at approximately 1.967 eV probably connected to a nitrogen-related defect center.