I. Tittonen - Academia.edu (original) (raw)
Papers by I. Tittonen
Nanotechnology, 2013
A novel aluminum oxide (Al2O3) hard mask fabrication process with nanoscale resolution is introdu... more A novel aluminum oxide (Al2O3) hard mask fabrication process with nanoscale resolution is introduced. The Al2O3 mask can be used for various purposes, but in this work it was utilized for silicon patterning using cryogenic deep reactive ion etching (DRIE). The patterning of Al2O3 is a two-step process utilizing focused ion beam (FIB) irradiation combined with wet chemical etching. Gallium (Ga(+)) FIB maskless patterning confers wet etch selectivity between the irradiated region and the non-irradiated one on the Al2O3 layer, and mask patterns can easily be revealed by wet etching. This method is a modification of Ga(+) FIB mask patterning for the silicon etch stop, which eliminates the detrimental lattice damage and doping of the silicon substrate in critical devices. The shallow surface gallium FIB irradiated Al2O3 mask protects the underlying silicon from Ga(+) ions. The performance of the masking capacity was tested by drawing pairs consisting of a line and an empty space with varying width. The best result was seven such pairs for 1 μm. The smallest half pitch was 59 nm. This method is capable of arbitrary pattern generation. The fabrication of a freestanding single-ended tuning fork resonator utilizing the introduced masking method is demonstrated.
2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), 2018
The fundamental research of many-body interactions and coherent transport of single particle elem... more The fundamental research of many-body interactions and coherent transport of single particle elementary excitations exploiting strong-light matter interactions in artificial molecular metamaterials for sensing having practical technological relevance is addressed. Confinement and coherent transport of elementary electron-hole excitations are directly monitored by high-spectral-resolution micro-Raman and photoluminescence spectroscopes in isolated semiconductor quantum dots. Crystalline nanostructures of nc-Si/SiO2 quantum dots as well as their functionalization by biomolecules with fabrication of nano-metamaterials will be considered. It has been found that these complexes are unique objects for the elucidation of the specific features in the manifestation of new quantum-size effects in biomacromolecules. It has been demonstrated that the possibility exists of detecting and recording in such nano-biomacromolecule metamaterials spectrally selective resonance enhancement of Raman scattering intensity in fluctuations of nucleotide molecules due to coherent nonradiative transfer of a photoexcited electron and a hole at the interface of the complex. This dynamic optical imaging of spectral responses can be of applied interest for the development of nanobiophotonic technologies for development label-free probes in a broader perspective for vital applications including early diagnosis of diseases at the molecular level.
Applied Nanoscience, 2021
Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhanc... more Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhance the electrocatalytic and photocatalytic activity of the films. Herein, the different approaches of synthesis procedure of Pt-and Pt,N-TiO 2 films were used to investigate their effect on the platinum oxidation states. The resulting different species of Pt led to the changes in the electronic structure of TiO 2 , with consequent bandgap narrowing, anodic shift of the flat band potential, and cathodic shift of the valence band The quantum yield efficiency was correlated with Pt 0 atomic content and the relative atomic content of Pt n+-O-Ti fragments, whereas its decrease for some samples can be caused by the presence of N and Pt n+. The highest response for N 2 O photocatalytic decomposition was observed over Pt,N-TiO 2 films. The presence of metal and non-metal species in TiO 2 structure resulted in synergistic effect including (1) inhibition of recombination of the electrons and holes and (2) narrowing of the bandgap. Electrocatalytic properties in hydrogen and oxygen evolution reactions were improved by Pt doping. The formed Pt 2+-O-Ti bonds rather than Pt nanoparticles are suggested to be responsible for the highest electrocatalytic activity. The additional UV exposure of the electrodes led to Pt NPs aggregation as a result of photodeposition of Pt ions. The mechanism of the Pt 2+ photoreduction in TiO 2 structure is proposed.
Physics Subject Headings (PhySH)
Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326)
We have used the powerful technique of THz time-domain spectroscopy' (TDS) to measure the abs... more We have used the powerful technique of THz time-domain spectroscopy' (TDS) to measure the absorption and dispersion of spectrally dense vapors of symmetric top molecules Because of the high sensitivity and dynamic range of this technique we can observe extremely small contributions in the low frequency wing of the rotational absorption band which originate from the inversion of molecules due to collision induced tunneling between the two states of symmetry Since in methyl halides and ammonia the respective tunneling or inversion frequency is very low, even at moderate pressures the line-width due to pressure broadening of such inversion lines is large compared to the center frequency which can be assumed to be zero. Therefore, the perturbation the molecule experiences when undergoing a collision enables the inversion transition to occur with the corresponding absorption of radiation Thus only molecular collisions, which cause an almost continuous broadening of the liner up to frequencies in the far infrared, permit measuring the inversion o f molecules as a broad background absorption and dispersion However, measurement of these spectra is complicated by the overlapping rotational band structure ofthe molecule which at its maximum is orders of magnitude larger. Alternatively the collisionally broadened inversion lines at zero frequency can be considered a s a Debye type absorption due to the stationary or non-rotating permanent dipole moment reorienting during a molecular collision With the newly developed terahertz beam sources, producing subpicosecond pulses of THz radiation, a new and wide frequency range for time and frequency domain studies of molecular vapors is available. For the first time this permits determination of the low frequency inversion line absorption simultaneously with the rotational manifold out to the far wings. Standard collision theory predicts a line-shape for a pressure broadened line with zero transition frequency which is given by the Dcbye theory and is distinguished by a broad, constant absorption and flat phase shift at the higher frequencies However, such absorption would cause an unacceptable large additional contribution in the high frequency wing that is in disagreement with our broad bandwidth measurements and cannot completely explain the observed spectrum in the low frequency wing. In arder to explain this discrepancy we have applied a new molecular response theory' which was developed for rotational transitions but also holds for the inversion lines. Compared to conventional collision theories, it additionally includes the molecular response of polar molecules to an external electric field over the duration of a collision. With a response time of the order of 200 fs the absorption shows a well restricted maximum at 150 GHz and only causes a significant attenuation in this frequency range, eliminating the non-physical 'Debye plateau". Using this new lineshape, excellent agreement between measurement and calculation is obtained.
Il Nuovo Cimento D, 1996
Summary We have studied the time dependence of Mössbauer absorption in a magnetically soft sampl... more Summary We have studied the time dependence of Mössbauer absorption in a magnetically soft sample of Fe18Ni82 permalloy under the influence of a radio-frequency (r.f.) magnetic field. Absorption was measured as a function of the r.f. field phase at specific gamma-ray energies. We have shown that measuring the time dependence of absorption makes it possible to differentiate between purely magnetic and magnetoacoustic modulation mechanisms even in cases where clear distinction is not visible in conventional energy domain spectra.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
ABSTRACT A method to realize UV lasers at 374 nm and 280 nm is demonstrated. A pump laser for the... more ABSTRACT A method to realize UV lasers at 374 nm and 280 nm is demonstrated. A pump laser for the SHG and SFG processes is a Nd:YAG laser at 1123 nm. The laser uses a Cr:YAG crystal as a passive Q-switch. To the best of our knowledge, this laser has not earlier been used to produce UV wavelengths. The laser is frequency doubled using a KTA crystal. Frequency conversions to 374 nm and 280 nm light were realized with BIBO and BBO crystals, respectively. The peak powers at 280 nm and 374 nm were 100 W and 310 W, and pulse lengths 6.4 ns and 7.7 ns respectively.
Physical Review B, 1995
ABSTRACT
2003 European Quantum Electronics Conference. EQEC 2003 (IEEE Cat No.03TH8665), 2003
Sensors and Actuators A: Physical, 2008
2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, 2008
ABSTRACT The down-conversion performance of a multimodal microelectromechanical mixer-filter is i... more ABSTRACT The down-conversion performance of a multimodal microelectromechanical mixer-filter is improved over 30 B by parametric amplification. The input signal is an AM-modulated signal with a carrier frequency of 0.5 Hz. The obtained amplification is shown to depend on the particular eigenmode in predetermined way due to the configuration of the electrodes used to excite and amplify the resonance.
A numerical model for the squeezed-film damping between moving rigid, rectangular surfaces is pre... more A numerical model for the squeezed-film damping between moving rigid, rectangular surfaces is presented. The emphasis is on the nontrivial boundary conditions for the flow, accounting for the finite acoustic impedance of the surrounding gas at the borders. The previously published electrical-equivalent macro model is modified to account for the end effects. The model is usable in simulating the circuit level and the system level behaviour of gas-damped devices in the time-and frequency domains.
TRANSDUCERS 2007 - 2007 International Solid-State Sensors, Actuators and Microsystems Conference, 2007
ABSTRACT A fast, dry micro fabrication process combining atomic layer deposition, electron beam l... more ABSTRACT A fast, dry micro fabrication process combining atomic layer deposition, electron beam lithography and cryogenic deep reactive ion etching (DRIE) is presented. The process utilizes atomic layer deposited ultra-thin (tax < 5 nm) aluminum oxide (Al2O3) films as hard mask for the DRIE that is used for both vertical cavity and dry release etching. The use of ultra-thin films can be explained by the extremely high selectivity (1:70 000) between Al2O3 and silicon. The process rules and limitations are carefully analyzed and in order to test the process, multiresonant tuning fork resonators are fabricated.
Design, Test, Integration, and Packaging of MEMS/MOEMS 2002, 2002
Mechanical oscillators that have a stable resonance with high quality factor have applications as... more Mechanical oscillators that have a stable resonance with high quality factor have applications as reference oscillators, sensors and in even very sophisticated high- precision experiments for observing quantum effects. In order to obtain a high quality factor the mechanical energy dissipation has to be minimised. At atmospheric pressure the most significant loss mechanism is gas damping, but for an oscillator working in vacuum the major part of the mechanical energy losses is caused by the coupling to the support structure and by internal friction which in turn is a result of a variety of physical mechanisms like thermoelastic effects and phonon scattering. Thus a great attention should to be paid to the material choice and the oscillator design.
Frequency Standards and Metrology, 2002
ABSTRACT An all-optical RF standard based on dark states of 85Rb atoms has been developed. With t... more ABSTRACT An all-optical RF standard based on dark states of 85Rb atoms has been developed. With this system we were able to measure ultra-narrow optically induced hyperfine dark resonances below 20Hz(Q-v alue &gt; 1.5 × 108). The frequency of a signal generator was stabilized to the dark resonance giving a relative frequency stability (square root of Allan variance) of 3.5 × 10−11τ−1/2 (1 s &lt; t &lt; 2000 s). The best stability reached at an integration time of t = 2000 s was 6.4 × 10−13, which is sufficient for many high-precision applications. The frequency shifts caused by various experimental parameters were also studied.
Physica Scripta, 2014
ABSTRACT The incoherent light emission from semiconductor nanostructures is investigated by deriv... more ABSTRACT The incoherent light emission from semiconductor nanostructures is investigated by deriving equations for semiconductor luminescence. The obtained formulation is independent of the particular structure geometry and mode functions of the quantized light. We demonstrate the importance of these results for a general quantum-ring system, the effective dimensionality of which is between zero and one.
Physical Review B, 1995
ABSTRACT
Nanotechnology, 2013
A novel aluminum oxide (Al2O3) hard mask fabrication process with nanoscale resolution is introdu... more A novel aluminum oxide (Al2O3) hard mask fabrication process with nanoscale resolution is introduced. The Al2O3 mask can be used for various purposes, but in this work it was utilized for silicon patterning using cryogenic deep reactive ion etching (DRIE). The patterning of Al2O3 is a two-step process utilizing focused ion beam (FIB) irradiation combined with wet chemical etching. Gallium (Ga(+)) FIB maskless patterning confers wet etch selectivity between the irradiated region and the non-irradiated one on the Al2O3 layer, and mask patterns can easily be revealed by wet etching. This method is a modification of Ga(+) FIB mask patterning for the silicon etch stop, which eliminates the detrimental lattice damage and doping of the silicon substrate in critical devices. The shallow surface gallium FIB irradiated Al2O3 mask protects the underlying silicon from Ga(+) ions. The performance of the masking capacity was tested by drawing pairs consisting of a line and an empty space with varying width. The best result was seven such pairs for 1 μm. The smallest half pitch was 59 nm. This method is capable of arbitrary pattern generation. The fabrication of a freestanding single-ended tuning fork resonator utilizing the introduced masking method is demonstrated.
2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials), 2018
The fundamental research of many-body interactions and coherent transport of single particle elem... more The fundamental research of many-body interactions and coherent transport of single particle elementary excitations exploiting strong-light matter interactions in artificial molecular metamaterials for sensing having practical technological relevance is addressed. Confinement and coherent transport of elementary electron-hole excitations are directly monitored by high-spectral-resolution micro-Raman and photoluminescence spectroscopes in isolated semiconductor quantum dots. Crystalline nanostructures of nc-Si/SiO2 quantum dots as well as their functionalization by biomolecules with fabrication of nano-metamaterials will be considered. It has been found that these complexes are unique objects for the elucidation of the specific features in the manifestation of new quantum-size effects in biomacromolecules. It has been demonstrated that the possibility exists of detecting and recording in such nano-biomacromolecule metamaterials spectrally selective resonance enhancement of Raman scattering intensity in fluctuations of nucleotide molecules due to coherent nonradiative transfer of a photoexcited electron and a hole at the interface of the complex. This dynamic optical imaging of spectral responses can be of applied interest for the development of nanobiophotonic technologies for development label-free probes in a broader perspective for vital applications including early diagnosis of diseases at the molecular level.
Applied Nanoscience, 2021
Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhanc... more Co-doping of titania by N and Pt species was employed to tune the electronic structure and enhance the electrocatalytic and photocatalytic activity of the films. Herein, the different approaches of synthesis procedure of Pt-and Pt,N-TiO 2 films were used to investigate their effect on the platinum oxidation states. The resulting different species of Pt led to the changes in the electronic structure of TiO 2 , with consequent bandgap narrowing, anodic shift of the flat band potential, and cathodic shift of the valence band The quantum yield efficiency was correlated with Pt 0 atomic content and the relative atomic content of Pt n+-O-Ti fragments, whereas its decrease for some samples can be caused by the presence of N and Pt n+. The highest response for N 2 O photocatalytic decomposition was observed over Pt,N-TiO 2 films. The presence of metal and non-metal species in TiO 2 structure resulted in synergistic effect including (1) inhibition of recombination of the electrons and holes and (2) narrowing of the bandgap. Electrocatalytic properties in hydrogen and oxygen evolution reactions were improved by Pt doping. The formed Pt 2+-O-Ti bonds rather than Pt nanoparticles are suggested to be responsible for the highest electrocatalytic activity. The additional UV exposure of the electrodes led to Pt NPs aggregation as a result of photodeposition of Pt ions. The mechanism of the Pt 2+ photoreduction in TiO 2 structure is proposed.
Physics Subject Headings (PhySH)
Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326)
We have used the powerful technique of THz time-domain spectroscopy' (TDS) to measure the abs... more We have used the powerful technique of THz time-domain spectroscopy' (TDS) to measure the absorption and dispersion of spectrally dense vapors of symmetric top molecules Because of the high sensitivity and dynamic range of this technique we can observe extremely small contributions in the low frequency wing of the rotational absorption band which originate from the inversion of molecules due to collision induced tunneling between the two states of symmetry Since in methyl halides and ammonia the respective tunneling or inversion frequency is very low, even at moderate pressures the line-width due to pressure broadening of such inversion lines is large compared to the center frequency which can be assumed to be zero. Therefore, the perturbation the molecule experiences when undergoing a collision enables the inversion transition to occur with the corresponding absorption of radiation Thus only molecular collisions, which cause an almost continuous broadening of the liner up to frequencies in the far infrared, permit measuring the inversion o f molecules as a broad background absorption and dispersion However, measurement of these spectra is complicated by the overlapping rotational band structure ofthe molecule which at its maximum is orders of magnitude larger. Alternatively the collisionally broadened inversion lines at zero frequency can be considered a s a Debye type absorption due to the stationary or non-rotating permanent dipole moment reorienting during a molecular collision With the newly developed terahertz beam sources, producing subpicosecond pulses of THz radiation, a new and wide frequency range for time and frequency domain studies of molecular vapors is available. For the first time this permits determination of the low frequency inversion line absorption simultaneously with the rotational manifold out to the far wings. Standard collision theory predicts a line-shape for a pressure broadened line with zero transition frequency which is given by the Dcbye theory and is distinguished by a broad, constant absorption and flat phase shift at the higher frequencies However, such absorption would cause an unacceptable large additional contribution in the high frequency wing that is in disagreement with our broad bandwidth measurements and cannot completely explain the observed spectrum in the low frequency wing. In arder to explain this discrepancy we have applied a new molecular response theory' which was developed for rotational transitions but also holds for the inversion lines. Compared to conventional collision theories, it additionally includes the molecular response of polar molecules to an external electric field over the duration of a collision. With a response time of the order of 200 fs the absorption shows a well restricted maximum at 150 GHz and only causes a significant attenuation in this frequency range, eliminating the non-physical 'Debye plateau". Using this new lineshape, excellent agreement between measurement and calculation is obtained.
Il Nuovo Cimento D, 1996
Summary We have studied the time dependence of Mössbauer absorption in a magnetically soft sampl... more Summary We have studied the time dependence of Mössbauer absorption in a magnetically soft sample of Fe18Ni82 permalloy under the influence of a radio-frequency (r.f.) magnetic field. Absorption was measured as a function of the r.f. field phase at specific gamma-ray energies. We have shown that measuring the time dependence of absorption makes it possible to differentiate between purely magnetic and magnetoacoustic modulation mechanisms even in cases where clear distinction is not visible in conventional energy domain spectra.
CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 2009
ABSTRACT A method to realize UV lasers at 374 nm and 280 nm is demonstrated. A pump laser for the... more ABSTRACT A method to realize UV lasers at 374 nm and 280 nm is demonstrated. A pump laser for the SHG and SFG processes is a Nd:YAG laser at 1123 nm. The laser uses a Cr:YAG crystal as a passive Q-switch. To the best of our knowledge, this laser has not earlier been used to produce UV wavelengths. The laser is frequency doubled using a KTA crystal. Frequency conversions to 374 nm and 280 nm light were realized with BIBO and BBO crystals, respectively. The peak powers at 280 nm and 374 nm were 100 W and 310 W, and pulse lengths 6.4 ns and 7.7 ns respectively.
Physical Review B, 1995
ABSTRACT
2003 European Quantum Electronics Conference. EQEC 2003 (IEEE Cat No.03TH8665), 2003
Sensors and Actuators A: Physical, 2008
2008 IEEE 21st International Conference on Micro Electro Mechanical Systems, 2008
ABSTRACT The down-conversion performance of a multimodal microelectromechanical mixer-filter is i... more ABSTRACT The down-conversion performance of a multimodal microelectromechanical mixer-filter is improved over 30 B by parametric amplification. The input signal is an AM-modulated signal with a carrier frequency of 0.5 Hz. The obtained amplification is shown to depend on the particular eigenmode in predetermined way due to the configuration of the electrodes used to excite and amplify the resonance.
A numerical model for the squeezed-film damping between moving rigid, rectangular surfaces is pre... more A numerical model for the squeezed-film damping between moving rigid, rectangular surfaces is presented. The emphasis is on the nontrivial boundary conditions for the flow, accounting for the finite acoustic impedance of the surrounding gas at the borders. The previously published electrical-equivalent macro model is modified to account for the end effects. The model is usable in simulating the circuit level and the system level behaviour of gas-damped devices in the time-and frequency domains.
TRANSDUCERS 2007 - 2007 International Solid-State Sensors, Actuators and Microsystems Conference, 2007
ABSTRACT A fast, dry micro fabrication process combining atomic layer deposition, electron beam l... more ABSTRACT A fast, dry micro fabrication process combining atomic layer deposition, electron beam lithography and cryogenic deep reactive ion etching (DRIE) is presented. The process utilizes atomic layer deposited ultra-thin (tax < 5 nm) aluminum oxide (Al2O3) films as hard mask for the DRIE that is used for both vertical cavity and dry release etching. The use of ultra-thin films can be explained by the extremely high selectivity (1:70 000) between Al2O3 and silicon. The process rules and limitations are carefully analyzed and in order to test the process, multiresonant tuning fork resonators are fabricated.
Design, Test, Integration, and Packaging of MEMS/MOEMS 2002, 2002
Mechanical oscillators that have a stable resonance with high quality factor have applications as... more Mechanical oscillators that have a stable resonance with high quality factor have applications as reference oscillators, sensors and in even very sophisticated high- precision experiments for observing quantum effects. In order to obtain a high quality factor the mechanical energy dissipation has to be minimised. At atmospheric pressure the most significant loss mechanism is gas damping, but for an oscillator working in vacuum the major part of the mechanical energy losses is caused by the coupling to the support structure and by internal friction which in turn is a result of a variety of physical mechanisms like thermoelastic effects and phonon scattering. Thus a great attention should to be paid to the material choice and the oscillator design.
Frequency Standards and Metrology, 2002
ABSTRACT An all-optical RF standard based on dark states of 85Rb atoms has been developed. With t... more ABSTRACT An all-optical RF standard based on dark states of 85Rb atoms has been developed. With this system we were able to measure ultra-narrow optically induced hyperfine dark resonances below 20Hz(Q-v alue &gt; 1.5 × 108). The frequency of a signal generator was stabilized to the dark resonance giving a relative frequency stability (square root of Allan variance) of 3.5 × 10−11τ−1/2 (1 s &lt; t &lt; 2000 s). The best stability reached at an integration time of t = 2000 s was 6.4 × 10−13, which is sufficient for many high-precision applications. The frequency shifts caused by various experimental parameters were also studied.
Physica Scripta, 2014
ABSTRACT The incoherent light emission from semiconductor nanostructures is investigated by deriv... more ABSTRACT The incoherent light emission from semiconductor nanostructures is investigated by deriving equations for semiconductor luminescence. The obtained formulation is independent of the particular structure geometry and mode functions of the quantized light. We demonstrate the importance of these results for a general quantum-ring system, the effective dimensionality of which is between zero and one.
Physical Review B, 1995
ABSTRACT