Display Technologies

Phosphor plays a key role to obtain white light as for blue LED + phosphor and near ultraviolet LED + phosphors. In order to improve high bright white LEDs, it is necessary that the whole phosphor particle emits light homogeneously. When measuring with CL the phosphor used as white LED, the area which does not emit light in phosphor particle can be observed. CL system is used for evaluation of non-luminescent area to improve luminescent efficiency and characteristics.

Phase Modulated Spectroscopic Ellipsometry is an excellent technique for the highly accurate characterization of complete TFT-LCD device. The technique allows the determination of film thickness, optical properties but also more complex properties such as graded or anisotropic layers and effect of dopants. In the flat panel industry the pressure to reduce manufacturing coasts is and reliable metrology tools are required to control the different steps of the process. Spectroscopic ellipsometry is a non-destructive technique which presents advanced capabilities and proven reliability tailored for qualification and on-line production control.

Raman spectroscopy is a very well suited technique to determine both Ge fraction and strain in SiGe layers and Si cap layers. Moreover the possibility of using both UV and visible excitation lines on the same instrument is essential to study structures made up of a Silicon cap layer on top of a SiGe layer. The relative Ge content in the constant Si1-xGex layer is calculated from the visible Raman spectrum and the strain of the cap Si layer is derived from the UV Raman spectrum.

Liquid Crystal Modulation Spectroscopic Ellipsometry is an excellent technique for the highly accurate characterization of the compound semiconductor heterostructure AlGaN / GaN. Using the MM-16 spectroscopic ellipsometer it is a straightforward procedure to determine the film thickness and optical dispersions of the complete structure even where the film is several microns thick. The detailed knowledge of the optical parameters of AlGaN alloys is crucial for example for the design of opto-electronic devices. Furthermore, from the optical parameters a calibration curve could be constructed to provide a rapid and efficient determination of the Al content in the AlGaN layers. Thus Spectroscopic Ellipsometry also proves a non-destructive technique for AlGaN alloy composition determination. This method can be equally applied to other compound emiconductors such as SiGe, II-VI semiconductors or classical III-V semiconductors.

PP-TOFMS is a fast and reliable technique for depth profiling of rare earth doped ZnO thin films. Tb and Eu profiles are obtained with high sensitivity and high depth resolution. This type of information is typically provided by SIMS, RBS or depth profiling XPS but not as rapidly and readily and at a higher cost. Such profiles turn out to be powerful complementary information to understand photoluminescence data. This example extends to similar materials for photonics (lighting, display, solar energy industries) applications such as other wide bandgap semiconductors (SiC, GaN...), nitrides and oxynitrides layers, silicon nano-objects, glasses... doped with Yb, Y, Sm, Er, Nd, Pr, and Tm...

For multilayer structures it is always helpful and often necessary to know the properties of each film. Using the Jobin Yvon UNISEL NIR it is a straightforward procedure to investigate the thickness and optical properties of the complete PDP structure. To ensure high yields in quality and quantity the FF-1000 ellipsometer is dedicated to the flat panel industries with a fully automated large area sample stage able to accept samples up to 1000 mm x 1000 mm. This accurate, automated thin film metrology tool delivers both unique performance and proven reliability for online quality control of production processes.

The Fluorolog-QM fluorescence spectrometer with an integrating sphere option is an excellent choice for PLQY measurements in NIR. The K-Sphere is very convenient and easy to use, as it couples directly to the sample compartment optics and allows a use of external light sources, such as DPSS lasers, which can be attached to the front of the sample compartment. The sphere has holders for cuvettes, slides and powders that can be easily interchanged. The results demonstrate very good reproducibility and precision for NIR PLQY measurements spanning almost two orders of magnitude. Based on multiple measurements, the demonstrated PLQY standard deviations range from 1.3% for high QY value (77%) to 6.4% for the QY below 1%.

Spectroscopic Ellipsometers are optical thin film measurement tools for determining film thickness and optical constants (n,k) of thin film structures. They are widely used in the microelectronics, display, photonics, photovoltaics, lighting, optical and functional coating, biotechnology industries. When compared with other optical metrology instruments the unique strength of spectroscopic ellipsometers are based on their highly precise and simple experimental measurements plus physical and material information derived from optical constants characterization.

The new Fluorolog-QM spectrofluorometers, due to their modularity and advanced software and a universal interface, are an ideal choice for studying multiple aspects of upconversion. This technical note illustrates the use of Fluorolog-QM-75-21 for spectral and time-resolved characterization of these materials.

Phase Modulated Spectroscopic Ellipsometry is an excellent technique for the highly accurate characterization of complete OLED stacks. The technique allows the determination of film thickness, optical properties and the effect of dopants to the active layers. For very high throughput applications where large area flat panels are to be characterized in a production environment the Jobin Yvon FF-1000 ellipsometer has a fully automated sample stage able to accept samples up to 1000 mm x 1000 mm. This accurate, automated thin film metrology tool delivers both unique performance and proven reliability for on-line quality control of production processes.

The characterization of synthetic CVD diamond material by hyperspectral cathodoluminescence spectroscopy and imaging allows the detection and accurate location of the promising NV luminescent point defects for innovative solid-state quantum mechanical systems. In this work we performed CVD epitaxial growth on a pattern of micro-pillars etched on a diamond substrate. Cathodoluminescence (CL) analysis revealed that NV centres were successfully localized at the edges of the pillars.

High-k dielectrics are under investigation to replace the conventional SiO2 or SiOxNy gate dielectric in many applications of Complementary Metal Oxide Semiconductor (CMOS) devices. Hafnium aluminium oxides (HfAlO) were investigated in this study as they fulfill the physical properties required for such applications. The structure and composition of hafnium aluminate films as well as the HfAlO / Si interface play a very important role for the optimization of CMOS devices. For this study complementary optical techniques were used. VUV Spectroscopic ellipsometry and infrared spectroscopy (FTIR-ATR) provide accurate characterization of thin film thickness and optical properties near and above the bandgap.

In this Application Note Spectroscopic Ellipsometry, a standard optical characterization technique used to measure multi-layered thicknesses and optical constants (n,k), has been successfully used to characterize encapsulated OLED devices. This report also investigates the aging process of OLED. Spectroscopic ellipsometry is a powerful technique to characterize the thickness and optical constants of encapsulated OLED devices. For the case of non-transparent encapsulation the combination of ellipsometric measurements via the glass substrate and the powerful modelling features of DeltaPsi2 software make it possible to analyze “this reverse sample”.

The threading dislocation occurs easily in GaN crystal grown on sapphire substrates. It is said that this is caused by the large lattice mismatch of sapphire and GaN. The crystal may seem to be uniform in the SEM image, but the dark spot such as the threading dislocation can be observed when measuring the CL intensity image at the wavelength (362nm) which corresponds to the band edge emission.

Spectroscopic ellipsometry is an excellent technique for the highly accurate characterization of TFT-LCD display panels based on a-Si and LTPS technologies. Owing to the sensitivity of the UVISEL spectroscopic ellipsometer and the advanced modeling features included in the DeltaPsi2 software it is possible to detect in a multistack different a-Si layers processed by various methods. Moreover the spectroscopic ellipsometry measurements allow determination of the grain size of p-Si films and illustrate the ability to characterize the crystallinity of silicon with high accuracy.

OLED technology is playing an important role in display technology since it offers several advantages compared to LCD technology among which its efficiency and high display quality, a high contrast rate, lower energy consumption, etc. Furthermore, this technology has an ecological aspect since it uses organic recyclable materials. However the improvement of the performances of the devices produced by these technologies requires a precise knowledge of their optical and structural properties that could be provided by spectroscopic ellipsometry. This non destructive and sensitive optical technique is able to characterize layers with thicknesses of some angstroms and provides information regarding the state of the surface, the microstructure of composite materials, etc.

Driven by applications like LED-backlit TVs and solid-state lighting, the global LED market is growing rapidly. The main challenges for general LED lighting include reducing overall production costs and increasing efficiency and lifetimes. The performance of a LED which is characterized by its wall-plug efficiency depends on the design and overall material properties of the LED thin film structure. Ellipsomentry may be used for the accurate determination of the thickness and optical constants of the LED device for both research and industrial applications. Accurate control of thickness and refractive index is vital for the optimization of device properties and for industrial quality control.