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TECHNOLOGY FOR CRYSTAL GROWTH and SAMPLE CHARACTERIZATION

A- CRYSTAL GROWTH TECHNOLOGY

A1.-CZOCHRALSKI, WITH DIAMETER CONTROL

The Czochralski (CZ) furnace equipment consist of a compact set-up for growing a great variety of single crystals, such as Lithium Niobate, pure and doped, bulk Periodic Poled Lithium Niobate, oxides, alkaly halides, fluorides (with control atmosphere) and others materials. All the equipment is controlled by a personal computer, which monitors the entire growth process. The set-up contains a typical PID program and an innovative fuzzy-logic control program developed in our lab, using our experience in the materials field for more than 20 years. All the phases of the growth process can be controlled such as the shoulder formation, the diameter of the crystal, the growth parameters, etc. The furnace works up to 1400ºC. With some modifications it is possible to use the equipment like a Liquid Phase Epitaxy furnace. The Crystal Growth Lab. is equipped with six Czochralkski with control diameter

CZ

   

A2.-VERTICAL GRADIENT FREEZE TECHNIQUE FOR THE GROWTH OF HIGH QUALITY SEMICONDUCTOR CRYSTALS

The Vertical Gradient Freeze (VGF) equipment is currently used for high quality CdZnTe (CZT) single crystals. The total equipment was controlled by home made software and we can able to maintain the precise temperature for the complete growth. In this technique, the temperature profile is adapted continuously to the growth process, without any ampoule translation.

The Crystal Growth Lab. is equipped with two VGF equipments, of one and two inches ampoule diameter. For the two inch diameter furnace, a numerical simulation model of the furnace and crystal growth has been created and validated using commercial codes, and has been used in conjunction with experimental results to optimize the process for the fabrication of high quality CZT crystals.

CZT

VGF Simulation


   

A3.-OSCILLATORY BRIDGMAN

The Oscillatory Bridgman equipment consist in a two zone zones furnace which can oscillate alternatively till a maximum of 90º in order to get a good mixture of all the chemicals located in the growth ampoule. Prior of the growth process, the ampoule oscillates during a limit time at a programmed oscillation speed. After this process, the ampoule is lowered down at a growth speed from 0.3 till 10 mm/h. The equipment is totally computerized. This equipment is currently used for the growth of bulk III-V compounds (In, Sb, Ga). The Crystal Growth Lab. is equipped with two oscillatory Bridgman apparatus.

Bridgman

   

A4.-FLUX EQUIPMENT

The flux equipment is a totally isolated box with three Temperature Controllers and with a set of 8 thermocouples to monitor the temperature in differents places. The furnace is made of Kanthal resistance with a maximum temperature of work of 1100 ºC. The equipment is prepared for growing materials using the flux method.

FLUX EQUIPMENT

   

A5.-CLOSED SPACE VAPOR TRANSPORT

The Closed Space Vapor Transport (CSVT) is a horizontal chamber for multideposition of three layers on a given substrate at different temperatures. The substrate is displaced manually along the growth process. The CSS is used for growing CdTe solar cells. The Crystal Growth Lab is equipped with one CSVT-B for deposition of one layer, and a second CSVT-A for deposition of three layers without breaking the vacuum at controlled atmosphere.

Vapor

 
 

A6.-LOW ENERGY ION IRRADIATION

The Low Energy Ion Sputtering (LEIS) system is equipped with a vacuum chamber (10-6 Torr), including a turbo pump, rotary pump, piranni and penning vacuum gauges. The system is also equipped with a Specs Ion gun enabling reaching energies up to 5 kV. The sample holder contains a heater enabling sample temperatures during irradiation up to 300 ºC.

Low Energy Ion Irradiation

A7.- HEAT EXCHANGED METHOD AND DIRECTIONAL SOLIDIFICATION EQUIPMENT

A 60 kg casting furnace for the production of high quality silicon ingots for photovoltaic applications is currently under construction at the Crystal Growth Laboratory. The furnace, which will grow ingot in a G4 quartz crucible, will combine Heat Exchange Method (HEM) and Directional Solidification System (DSS) technologies, which can be used separately or in tandem, allowing for great adaptability and versatility in the crystal growth process. In combination with numerical simulations of the furnace with commercial codes, the crystal growth process will be optimized for the production of high quality multicrystalline silicon (mc-Si) and seeded mono-like silicon (ml-Si).

Heat Simulation

HEM DSS UAM 1

HEM DSS UAM 2

A8.CLOSE SPACE SUBLIMATION (CSS) CHAMBER

The polishing machines are the most simple and cheapest version of a polishing machine for any material used in optical applications. Lapping and polishing processes can be easily done. The polishing machine is consequence of our experience in the preparation of materials from the past 20 years. The Crystal Growth Lab. is equipped with two polishing machines.

Sublimation


B- SAMPLE PREPARATION AND CHARACTERIZATION TECHNIQUES

B1- POLISHING MACHINES

The polishing machines are the most simple and cheapest version of a polishing machine for any material used in optical applications. Lapping and polishing processes can be easily done. The polishing machine is consequence of our experience in the preparation of materials from the past 20 years. The Crystal Growth Lab. is equipped with two polishing machines.


polishing

The MECHANICAL POLISHING Logitech PM5 Precision Lapping and Polishing Machine is a bench-top R&D scale system that yields reproducible results with the flexibility of working with many different materials. It is controlled through a joystick interface with an LCD screen display. It has an integral abrasive autofeed system and automatic lapping plate flatness control. The SMIF system includes the PP5 Precision Lapping and Polishing Jig which is used to hold samples of widely varied shape while they are polished. This jig allows precise control of the orientation of the sample to the polishing plane and fine adjustment of the load applied to the sample during polishing. It includes a thickness removal indicator and vacuum chuck.

polishing

 

The CHEMICAL POLISHING CP3000 is a chemical polishing machine for use with aggressive polishing media such as bromine methanol in addition to the more commonly encountered sodium hypochlorite based polishing fluids like Chemlox. The CP3000 machine is designed to be resistant to aggressive chemical polishing agents and consequently the teflon polishing fluid rack will withstand exposure to chemical polishing agents. The control module is separate from the machine so that it can be located outside the fume cabinet for safety. Typical applications for the CP3000 Chemical Polishing Machine are the final chemical etch polishing before device fabrication or epitaxial growth analysis

polishing

B2.-COREMA

Contacless Resistivity Mapping from Eurorad automatic equipment for measuring the volume resistivity of samples with a range of 10E5-10E10 ohm.cm

Corema

B3.-CUTTING MACHINES

The WELL diamond wire saw cutting machines Model 3032 and Model 3242 are available at CGL, in the horizontal or vertical cutting position. The "cutting tool" employed is a stainless steel wire with diamonds embedded into the surface of the wire. Both cutting machines are used for semiconductor materials.

cutting


B4.-IR MICROSCOPY

The IR MICROSCOPY system mainly consists of: An infrared back light, an IR sensitive CCD camera with long objective microscope lens and a 7.8x10.6 mm2 sensor with 2208x3000 pixels, with 3D translation stage. Different objectives are used for the characterization of the surface bulk crystals and Te inclusions, ranging from 1x to 50 x magnifications. By using the 3D translation stage, the system can perform a one, two, or three dimensional scan. At each XYZ position of the crystal, an image of the area is taken and saved, and then the translation stage moves to the next position where this is repeated. The system setup allowed us to acquire stacks of images, each focused at a different depth of the crystal. IR images were saved as monochrome high-resolution jpeg files and Image-pro Plus 6.0 software was used to calculate the sizes and concentrations of Te precipitates in the crystal.

IR

B5-ATOMIC FORCE MICROSCOPY

The Atomic Force Microscopy (AFM) is a Park Systems Atomic Force Microscope, Model XE 100. This sistem enables AFM analysis both in contact and non contact mode

Atomic Microscopy

B6-UV-IR ESPECTROMETER

The UV-IR spectrometer Perkin Elmer Lambda Spectrometer is used as characterization technique in the UV/NIR region (150-3500 ?m) of the visible spectrum.

Uv IR

B7- NANOPARTICLE PREPARATION

The Parr Autoclave (250 ml) is used for nanoparticle preparation at a max temperatures of 300 ºC and up to 300 Bar pressures

Nanoparticle

B8- GLOVE BOX FOR SAMPLE PREPARATION

The glovebox MBRAUN UNIlab hat is designed to manipulate objects where a separate atmosphere is desired, such as argon or nitrogen. The is a ready to operate workstation that includes a large main antechamber, vacuum pump and monochrome color Siemens PLC touch screen controller. In particular, the glovebox is used to weigh the starting material (Cd, Zn, Te) and to charge it inside the quarz ampoule for crystal growth at a controlled atmosphere in such a way that the 7N starting materials never are in air atmosphere.

Glove Box

 

B9-OTHER CHARACTERIZATION TECHNIQUES

Several characterization techniques are available at the SERVICIO DE INVESTIGACIÓN INTERDEPARTAMENTAL, SIDI, located at UAM, being a technical service for all the University staff.

http://www.uam.es/investigacion/servicios/sidi/

The most important facilities are: Induced Couple Plasma analysis (ICP-MS), High Resolution X ray Diffraction (HRXRD), Scanning Electron Microscopy (SEM),Transmission Electron Microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR), Total X-Ray Fluorescence (TXRF)

C- MATERIALS FOR RESEARCH

The Crystal Growth Lab. has grown hundreds of materials in the past years. Some examples are in this photo.

new crystals

Crystal Growth Materials

LiNbO3, LiNbO3:Er, LiNbO3:Fe, LiNbO3:Mg:Fe, Bi12TiO20, Bi12SiO20, Bi12GeO20, Bi4Ge3O12, Li2B4O7, NaCl, GaSb, CdTe

Crystal Growth Materials

LiNbO3, LiNbO3:Er, LiNbO3:Fe, Bi12TiO20, Bi12SiO20, Bi4Ge3O12, KCl:Eu, LiF, NaCl, CdTe

CZT Materials

CZT Materials

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