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Blistering And Waveguide Fomation In Optical Crystal Materials By Ion Lmplantation

Posted on:2016-01-18Degree:DoctorType:Dissertation
Country:ChinaCandidate:B X XiangFull Text:PDF
GTID:1108330461984364Subject:Condensed matter physics
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As a heavily investigated domain for material surface engineering and characterizations, ion beam technique has given rise to many key techniques for semiconductor industry in the past few decades. Rutherford Back Scattering/Channeling (RBS/Channeling), Elastic Recoil Detection Analysis (ERDA), Nuclear Reaction Analysis (NRA) and Secondary Ion Mass Spectroscopy (SIMS) have emerged as powerful and unique tools for surface and interface analysis. Ion implantation/irradiation has been widely used in the surface modifications of semiconductors, metals and insulators. It also plays important roles in fields of chemistry, medicine and metallurgy.The integrated photonics, which refers to the fabrication and integration of several photonic components into a single planar substrate, is a swiftly developing scientific domain ever since the end of the last century. As the basic elements of integrated photonic systems, optical waveguides are defined as high-refractive-index media surrounded by low-index layers/regions. The dimension of the waveguides is similar to the operating wavelength. The small size of waveguide structures offers high light intensity with respect to the bulk devices. The nonlinear frequency generation (second harmonic generation, optical parameter oscillation etc.), laser action (waveguide laser and amplifier) and optical soliton in waveguides have attracted lots of attentions in recent years. Up to now, several manufacturing methods have been employed to fabricate dielectric waveguide structures, including metal ion diffusion, ion exchange, thin film deposition, ion beam techniques, direct femtosecond laser writing, sol-gel and combinations of the above-mentioned methods. Among these, ion beam technique is widely used and still being studied for specific materials.Ion beam techniques offer intriguing versatility for fabrication of photonic guiding structures in numerous optical substrates, including crystals, glasses, semiconductors, and organic materials, by means of different ion implantation processes with diverse species, energies, and fluence. Several specific ion beam techniques have been used to fabricate photonic guiding structures. Direct ion implantation, Crystal ion slicing (CIS)/Smart cut and ion beam enhanced etching (IBEE) are representative examples. Direct ion implantation has been developed as a efficient method to fabricate waveguide structures in many optical crystals, ceramics, polymers, and glasses due to its accurate control of the depth and fluence of the ions, as well as the universal mechanism of waveguide formation. Combined with lithography and etching technique, direct ion implantation can fabricate various functional optical elements. Ion implantation can be divided into light ions (H and He) implantation and medium-heavy ions (such as C, O, Si, Ar and Cu etc.) implantation. The fluence of medium-heavy ion implantation can be 1-3 orders lower than that of light ion implantation. In general, medium-heavy ion implantation is a relatively more effective method. Now, swift heavy ion (heavy ions with energy usually between 20 MeV - several GeV) irradiation, as a new way to fabricate waveguides, attracts more and more attention.The CIS/Smart cut technique is a promising approach to fabricate the free standing films for various integration applications. Helium or hydrogen ions are implanted into the bulk seed wafer and stopped around a certain depth. After bonding to a suitable handle substrate, the implanted seed wafer is separated (sliced) at the implanted depth by using a wet etching or thermal splitting process. Light ion implantation induced blistering is the physical origin of CIS/Smart cut technique. Blistering is indeed a very common phenomenon, and it has been qualitatively understood in broad terms. H and He are hardly soluble in most materials, therefore they tend to segregate into cavities which grow and coalesce at high temperature. The gas pressure in the cavities finally deforms the surface under certain conditions.IBEE is a technique combination of ion implantation and chemical wet etching. It is a promising approach to fabricate ridge waveguide and other photonic microstructures. The mechanism of IBEE is somewhat similar to the wet-etching-related CIS technique. Considerably large numbers of defects are induced by the ion irradiation due to energy transfer to the crystal lattices, forming highly damaged or even amorphous regions in surface region. One of the direct consequences of the highly damaged regions is that the chemical resistance is considerably reduced so that these regions can be removed by wet chemical etchant.The efforts in this dissertation are devoted to the fabrication and characterization of the photonic guiding structures in optical materials by ion beam technique. The work in the dissertation methodologically divided into three portions:Crystal ion slicing/Smart cut, ion beam enhanced etching and waveguide formation by direct ion implantation.We report on the fabrication of LiNbO3 waveguide slabs with sub-micron thickness using He ion-induced splitting and the Cu-Sn bonding technique. The blistering/exfoliation time of implanted LiNbO3 was investigated as a function of annealing temperatures to reveal the activation energies during the splitting process. Defect-free waveguide films with large areas of several cm2 are consistently produced by using the inter-diffusion bonding of Cu-Sn interface. The fabricated film was characterized by the Rutherford Back Scattering/Channeling method and dark mode spectroscopy.The rutile single crystals were implanted by 200 keV He ions with a series fluence and annealed at different temperatures to investigate the blistering behavior. The near surface lattice deviation and lattice strain has been characterized by Rutherford Back Scattering/Channeling and X-ray diffraction measurements. Our investigations indicate that efficient blistering in rutile single crystal can be achieved by He ion implantation and the following thermal annealing.The KTaO3 single crystals were implanted by 190 keV He ions with a series fluence and annealed at different temperatures to investigate the blistering behavior. The substantial He out diffusion has been investigated, He depth distribution changes from an initially unimodal Gaussian form to a bimodal distribution. It was found that the blistering on KTaO3 surface region can be realized by He ion implantation with low fluence and the following thermal annealing.The ion-beam enhanced etching was achieved on z-cut LiNbO3 by oxygen, silicon and copper ions implantations with several MeV energies individually. The etching rate, depth and surface morphology were characterized by surface profilometer, metallurgical microscope and scanning electron microscope. The electronic energy loss induced by MeV ion implantation was found to be an efficient approach to realize the surface etching. The etching quality was determined by choosing appropriate ion species and fluence. Micro cracks can be avoided under appropriate choice of ion and fluence. High quality microstructures can be fabricated. Low loss ridge waveguides were fabricated and characterized in proton exchanged LiNbO3 planar waveguide. The transverse guiding was achieved by a combination of MeV ion implantation and the following wet etching. The etched surface morphology were characterized. The mode guiding behaviors at wavelengths of 632.8nm were demonstrated with propagation loss of 1.13 dB/cm.Low loss planar and channel waveguides in Pr3+ doped yttrium orthosilicate single crystals were fabricated by using 6MeV oxygen ion implantation. The fabricated surface guiding structure was characterized by prism coupling method. The relationship between the implantation induced index change and the implantation fluence has been investigated. The photoluminescence properties of the implanted samples were found to be well preserved with respect to the bulk, exhibiting possible applications for integrated quantum memory and laser generation devices.The planar waveguides were formed in magnesium doped stoichiometric LiNbO3 crystals by means of 4.5 MeV oxygen ion implantations at different fluence. The dark mode spectra were measured by the prism coupling method. The annealing behaviors of the formed waveguides were characterized by a series of annealing treatments. The Rutherford Back Scattering/Channeling technique was used to investigate the damage produced by the ion implantation.
Keywords/Search Tags:Ion implantation, Blistering, Optical waveguide, Ion-beam enhanced etching, Optical crystal
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