Observing the morphology of single-layered embedded silicon nanocrystals by using temperature-stable TEM membranes.

Sebastian Gutsch,Margit Zacharias,Daniel Hiller,Christian Kübel,Jan Laube

doi:10.3762/bjnano.6.99

Abstract

We use high-temperature-stable silicon nitride membranes to investigate single layers of silicon nanocrystal ensembles by energy filtered transmission electron microscopy. The silicon nanocrystals are prepared from the precipitation of a silicon-rich oxynitride layer sandwiched between two SiO2 diffusion barriers and subjected to a high-temperature annealing. We find that such single layers are very sensitive to the annealing parameters and may lead to a significant loss of excess silicon. In addition, these ultrathin layers suffer from significant electron beam damage that needs to be minimized in order to image the pristine sample morphology. Finally we demonstrate how the silicon nanocrystal size distribution develops from a broad to a narrow log-normal distribution, when the initial precipitation layer thickness and stoichiometry are below a critical value.

Highlights

Si nanocrystals (Si NC) are interesting for applications in third generation photovoltaics [1,2], light emitting diodes [3,4], lasers [5], but are envisioned to be used as non-volatile memories [6,7,8,9,10]
A faster and easier approach to measure the Si NC size, position and density is the use of in-plane energy-filtered transmission electron microscopy (TEM) (EFTEM) as was demonstrated for Si NCs formed by low energy Si ion implantation [10,26], plasma-enhanced chemical vapor deposition (PE-CVD) [27] or evaporation [28] followed by a high temperature annealing
We have demonstrated an approach using ultrathin TEM membranes and EFTEM imaging as a very versatile tool to study the morphology of Si NC ensembles in contrast to the limitation imposed by cross sectional TEM investigations [19,20,29]

Summary

Introduction

Si nanocrystals (Si NC) are interesting for applications in third generation photovoltaics [1,2], light emitting diodes [3,4], lasers [5], but are envisioned to be used as non-volatile memories [6,7,8,9,10]. A faster and easier approach to measure the Si NC size, position and density is the use of in-plane energy-filtered TEM (EFTEM) as was demonstrated for Si NCs formed by low energy Si ion implantation [10,26], plasma-enhanced chemical vapor deposition (PE-CVD) [27] or evaporation [28] followed by a high temperature annealing.

Results

Conclusion