A cauliflower structure is a granular film composed of spherical particles similar in size, each with numerous nanoscale nodules on its surface. The structure is produced during certain chemical vapour deposition (CVD) processes for diamond and silicon thin film growth. A classical account in terms of atomic unit deposition fails to explain the growth of such a cauliflower structure, as it requires a gas phase of much higher supersaturation than for onset of diffusion controlled growth. Another interesting and somewhat puzzling phenomenon encountered during a diamond CVD process is that while diamond is depositing on a graphite substrate, carbon atoms in the graphite itself are etched away into the vapour phase; that is, experience evaporation. Again, an elementary kinetic barrier mechanism fails to explain such CVD deposition of a less stable diamond phase combined with simultaneous evaporation of a stable graphite phase. In order to account for such puzzling CVD phenomena and others, a theory o...

Charged clusters in thin film growth

Effect of methane concentration on size of charged clusters in the hot filament diamond CVD process

The critical role of charged nanoclusters and nanoparticles in the growth of thin films and nanostructures by chemical vapour deposition (CVD) is reviewed. Advanced nanoparticle detection techniques have shown that charged gas-phase nuclei tend to be formed under conventional processing conditions of thin films and nanostructures by thermal, hot-wire and plasma CVD. The relation between gas-phase nuclei and thin film and nanostructure growth has not been clearly understood. In this review it will be shown that many films and nanostructures, which have been believed to grow by individual atoms or molecules, actually grow by the building blocks of such charged nuclei. This new growth mechanism was revealed in an attempt to explain many puzzling phenomena involved in the gas-activated diamond CVD process. Therefore, detailed thermodynamic and kinetic analyses will be made to draw the conclusion that the well-known phenomenon of deposition of less stable diamond with simultaneous etching of stable graphite should be an indication of diamond growth exclusively by charged nuclei formed in the gas phase. A similar logic was applied to the phenomenon of simultaneous deposition and etching of silicon, which also leads to the conclusion that silicon films by CVD should grow mainly by the building blocks of charged nuclei. This new mechanism of crystal growth appears to be general in many CVD and some physical vapour deposition (PVD) processes. In plasma CVD, this new mechanism has already been utilized to open a new field of plasma-aided nanofabrication.

https://iopscience.iop.org/article/10.1088/0022-3727/43/48/483001/pdf

Charged nanoparticles in thin film and nanostructure growth by chemical vapour deposition

Scale control by threshold treatment

The crystallization of NaCl in the presence of [Fe(CN)6]4- ions

A New Mechanism for the Crystallization and Growth of Ionic Crystals, with Special Reference to KCl in the Presence of Pb2+ Ions.

Methods for the determination of magnesium and aluminium, present as impurities, in A.R. alkali halides have been developed. Both ions were separated by co-precipitation in the form of their hydroxides, and improved spectrophotometric methods were used for their quantitative analysis.



These and other methods have been used to follow the purification of KCl by re-crystallization from aqueous solutions, and some illustrative observations are reported.

Studies on the Purification of Kcl.: II. Spectrophotometric Determination of Magnesium and Aluminium in A. R. Alkali Halides†

The calcium content of various KCl products was determined, using glyoxal-bis(2-hydroxyanil) as a specific colouring reagent. Some preliminary results of purification by crystallization are also reported.

Sarah Skurnik

Papers

A New Mechanism for the Crystallization and Growth of Ionic Crystals, with Special Reference to KCl in the Presence of Pb2+ Ions.

Studies on the Purification of Kcl.: II. Spectrophotometric Determination of Magnesium and Aluminium in A. R. Alkali Halides†

Spectrophotometric Determination of Ultramicro Quantities of Calcium in KCl

Spectrophotometric Determination of Lead in KCl Crystals