Surface State in Bi1.5Sb0.5Te1.7Se1.3 Nanoflakes

Surface State in Bi1.5Sb0.5Te1.7Se1.3 Nanoflakes Result of a study on the surface state in Bi1.5Sb0.5Te1.7Se1.3 nanoflakes 4.1 Introduction The recent discovery of topological insulators (TIs) has provided new route for producing low-dimensional relativistic electronic states. The exotic surface states of TIs have attracted the attention of scientists because of their fascinating physical properties and applicability in spintronics and quantum computations [24-28]. The unique surface states were confirmed by angle-resolved photoemission spectroscopy (ARPES) experiments and scanning tunneling microscopy (STM) on Sb2Te3, Bi2Te3, and Bi2Se3 [29-34]. Magnetotransport studies have also provided a clear picture of the topological surface state and the  ° Berry phase shift [35, 36],which gives rise to the immunity of Dirac fermions to localization. Bi2Te3 and Bi2Se3 are suitable candidates for TI studies because of their large energy gaps. Eg is approximately equal to 0.3 eV and 0.17 eV. However, the metallic bulk conduction of natural imperfections, such as vacancies or antisite defects in these materials, makes it difficult to probe surface Dirac fermions. Therefore, a high-insulating bulk state is a prerequisite for transport property studies of TIs. Substantial effort has made it possible to examine both the surface and the bulk channels either through electrical gating [36-42] or substitution doping [12-14, 42]. Recently, it was discovered that Bi2-xSbxTe3-ySey (BSTS) is a high-insulating bulk TI. BSTS exhibits a tetradymite structure, a low carrier concentration (2.3 Ãâ€" 1016 cm3), and a large bulk resistivity (8 ÃŽ © cm) because of the ordered occupation of Te/Se in the quintuple-layer unit [12, 13]. However, a reliable detection of surface quantum oscillations is difficult in BSTS flakes because of the inhomogeneous defect [12] and low surface mobility [40]. Thus, the low mobility in a bulk channel plays a crucial role in probing surface quantum oscillations. In this chapter, we report the observation of surface-dominated transport in the topological insulator BSTS nanoflakes. Shubnikov-de Hass (SdH) oscillations study on the 200-nm BSTS nanoflake indicates that the achievement of surface-dominated transport can be attributed its high surface mobility of 2602 cm2/Vs (top surface), 3657 cm2/Vs (bottom surface), and low bulk mobility of 12 cm2/V s, which is a much lower value than those reported [12-13, 40-41]. Besides, the nontrivial Dirac surface state was further confirmed by the weak anti-localization (WAL) effect and the semiconducting to metallic transport transformation as the thickness of the specimen was reduced to the thin film limit, in which a up to 90% contribution from the surface channel was estimated based on the thickness dependence of the electrical conductance and the result of the SdH oscillations. 4.2 Method BSTS single crystals nominally composed of Bi1.5Sb0.5Te1.7Se1.3 were grown by melting the mixture of Bi (99.999%), Sb (99.999%), Te (99.999%), and Se (99.999%) in sealed evacuated quartz tubes. First the mixture was slowly ramped up to 750  °C at a rate of 100  °C/h and kept at 750  °C for 12 h. It was then furnace cooled to room temperature at a rate of 100  °C/h. The sample was reground and sintered again. The same procedure was repeated three times to ensure sample homogeneity. Finally, the sample was heated to 800  °C for 48 h, then cooled to 500  °C and annealed for 96 h. The crystal structures of the samples were identified using powder X-ray diffraction and refined using the General Structure Analysis System (GSAS) software package equipped with the EXPGUI interface, as shown in Figure 4.1(a). Transport measurements were conducted using a Quantum Design Physical Property Measurement System (PPMS) and six-terminal Hall bar geometric specimens. The nanoflake specimens [Figure 4.1(b)] were mechanically exfoliated and transferred to the Si3N4 (200 nm)/Si substrate. The electrodes of the nanoflake were patterned using standard e-beam lithography and thermal evaporation of Ti/Au. Figure 4.1. (a) GSAS refinement of powder X-ray data of a BSTS crystal. Red circles represent experimental results, the green line represents calculated results, the blue line indicates the difference, and the Bragg peaks of the BSTS are shown by the vertical lines, where Rp, Rwp, and à ¯Ã‚ Ã‚ £2 represent the goodness factors. (b) The SEM image of a BSTS 160-nm nanoflake. 4.3 Results and discussion 4.3.1 Thickness and temperature dependence of resistance The considerable thickness dependence of electrical transport showed a transition from semiconducting to metallic behavior as the bulk content is reduced, as shown in Figure 4.2 (a). For the thick specimens, the thermal activation energies given by the Arrhenius law were 4.3 meV (140 ÃŽ ¼m), 3.5 meV (49 ÃŽ ¼m), and 2.37 meV (7 ÃŽ ¼m). The smaller activation energy of thinner specimens can be explained by the increasing contribution of surface states [12-13, 40-41]. In 140-ÃŽ ¼m BSTS, a significant deviation occurred below 20 K from the fitting to a three-dimensional variable-range hopping model (3D VRH) with Rxx is approximately exp[(T/T0)-1/4] [13], indicating the existence of a parallel metallic conduction of surface states [the inset in Figure 4.2 (a)]. According to Eq. 4.1, the total conductance G ° of a specimen with a thickness t can be formulated as G ° = Gs + à ¯Ã‚ Ã‚ ³bt, (4.1) where Gs is the surface sheet conductance, and ÏÆ'b is the bulk conductivity [38,42]. Gs =36.2 (e2/h) and à ¯Ã‚ Ã‚ ³b = 4.14 (e2/h) ÃŽ ¼m−1, which resulted from the fit of thickness dependence of conductance to Eq. 4.1. For a 200-nm nanoflake at 2 K, up to 90% of the contribution from the surface state was obtained, as shown in Figure 4.2 (b). Figure 4.2. (a) Temperature dependence of resistivity for BSTS specimens with thicknesses of 140 ÃŽ ¼m, 200 nm, 160 nm, and 80 nm. The inset shows the fit of 3D variable-range hopping to the 140-lm specimens. (b) Thickness dependence of sheet conductance; the red line is the fit with G ° = Gs + à ¯Ã‚ Ã‚ ³bt. The inset shows the fitting of the Arrhenius law to the 140-ÃŽ ¼m specimen. 4.3.2 Hall measurements of BSTS To understand the semiconductor-metallic transitions, we focus on the charge transport behavior (Figure 4.3) and temperature dependence Hall measurement results of 160 nm specimen (Figure 4.4). Because of that the thickness seems like to the critical in between semiconductor and metallic transition. In Figure 4.3 (a), we gives three regimes in the temperature profile, one can obtain the nanoflake specimen with 160 nm thick showing metallic behavior which contrasts to its bulk. In the regime I, the bulk conduction dominates, as the temperature decreases the resistance increased which shows a general narrow-gap semiconductor behavior this can be attributed to freezing of the impurity band carrier in the bulk [27]. The regime II reveals a typical metallic behavior signature, the resistance decreases as temperature reduced, this can be explained as reduce phonon scattering and nearly constant carrier density (shown in Figure 4.4 (a)) with a decreasing temperature. In regime III, when the temperature is lower than 10 K, a slightly increases in resistance due to the bulk carriers freeze out [28]. Hall mobility measurements provide more clearly picture to realize the thickness dependence charge transport as shown in Figure 4.4 (b). The reduction in the degree of disorder or impurity of specimens can be obtained in Figure 4.4 (b) that the mobility enhanced as thickness decreased and their different temperature dependence trends. In thinner specimens (160 and 80 nm) the mobility shows monotonically increasing as decreasing temperature, surface dominate transport should play a more important role in this manner. Figure 4.3. Temperature dependence of the normalized resistance of specimens. Figure 4.4 (a) Temperature dependence of the Hall measurement results of 160 nm thick specimen. (b) Thickness dependence of Hall mobility versus temperature curve. 4.3.3 Surface quantum oscillations (Shubnikov-de Haas oscillations) Because successive empting of Landau levels (LLs) provides the nth minima in à ¯Ã†â€™Ã‚ ³Rxx, the relation of the LL index n to the Fermi surface cross-section area AF can be described using the semiclassical Onsager equation: 2 ° (n + à ¯Ã‚ Ã‚ §) = AF Ä § / eB. For the Schrodinger electron case, à ¯Ã‚ Ã‚ § = 0, which results in a zero Berry phase. à ¯Ã‚ Ã‚ § = 1/2 indicates the case of the Dirac fermion of TIs, which results in a  ° Berry phase where the charge carrier is immune to localization. The temperature dependence of resistance for a 200-nm nanoflake shows à ¯Ã†â€™Ã‚ ³Rxx as a function of 1/B after a smoothing background subtraction, as shown in Figure 4.5 (a). Two sets of oscillation periods are marked; one with a black dashed line ([(à ¯Ã†â€™Ã‚ ³(1/B) = 0.041 T-1]) and the other with a blue dashed line (0.022 T-1) for the surfaces of the nanoflake specimen. The multicomponent nature of SdH oscillations originates from the Fermi-level positions of the two surfaces. If SdH oscillations are as a result of the two-dimensional electron gas (2DEG) formed with band bending near the surface, the corresponded carrier density differs in an order of magnitude [35] compared to the Hall measurement result [n3D = 3.5 à ¯Ã¢â‚¬Å¡Ã‚ ´ 101 8cm-3], which is obtained from the fit to low field B ( ±1T) data (Figure 4.5 (b)). Figure 4.5 (c) shows the LL fan diagram plotted in 1/B versus nth oscillation minima in à ¯Ã†â€™Ã‚ ³Rxx. The linear fit of the two-set SdH spectrum yields the intercepts of à ¯Ã‚ Ã‚ § = 0.48  ± 0.3 for Surface 1 and 0.49  ± 0.02 for Surface 2, where à ¯Ã‚ Ã‚ § values are closer to the theoretical value of 0.5 for ideal Dirac fermions. It is assumed that Surface 2 is the top surface because environmental contamination provides effective n-type doping [17] to the sample, which strongly influences the top surface. The specimens were closely stacked on the substrate to prevent the bottom surface from air contamination and electron-beam irradiation. Thus, the second set of SdH oscillations appears in the lower inversed field, shown in Figure 4.5 (a), which was probably from the top surface. In Figure 4.5 (c), the slope of one set of SdH oscillations provides the cross-section area of the Fermi surface [AF = 4.15 Ãâ€" 1017 m-2], and the Fermi wave number was = 0.0363 and the 2D surface carrier density was = 1.05 Ãâ€" 1012 cm-2 for the top surface (Surface 2). The second set of SdH oscillations resulted in AF = 2.32 Ãâ€" 1017 m-2 and = 0.02718 , and 0.58 Ãâ€" 1012 cm-2 for the bottom surface (Surface 1). Figure 4.5 (d) shows the fit of temperature dependence of SdH amplitudes to the Lifshitz-Kosevich (LK) theory [11, 43].The cyclotron mass mc = 0.075 me is the same as that reported [13]. Once mc is known, we can calculate the Fermi velocity and the Fermi level position to be vF = 5.6 Ãâ€" 105 m/s and EF = 134 meV above the Dirac point for the top surface and vF = 4.19 Ãâ€" 105 m/s and EF = 75 meV for the bottom surface. The high Fermi level position of the top surface is consistent with the results of environmental doping mentioned previously. Due to the multiple component nature, the Dingle temperature is difficult to extrapolate from the SdH amplitude; therefore, Eq. 4.2 is used to fit the resistance data to the LK theory , (4.2) where F is the frequency of SdH oscillations extracted from the slopes of Figure 4.5 (c), the thermal factor is , and the Dingle temperature is [11, 43]. The solid red line in Figure 4.5 (e) shows the optimal fitted results of à ¯Ã‚ Ã‚ § = 0.5 and à ¯Ã‚ Ã‚ ´ = 1.11 Ãâ€" 10-13 s for the top surface, and à ¯Ã‚ Ã‚ § = 0.35 and à ¯Ã‚ Ã‚ ´ = 1.56 Ãâ€" 10-13 s for the bottom surface. The fitted à ¯Ã‚ Ã‚ § values are close to theoretical value of 0.5 for ideal Dirac fermions. According to the Dingle analysis, the scattering time is approximately two to three times larger than that of the bulk BSTS [13]. Mobility is a measure of scattering time; therefore, it is possible to calculate the surface mobility ÃŽ ¼s = 2602 cm2V-1s-1 and the mean free path = 62 nm for the top surface, and ÃŽ ¼s = 3657 cm2V-1s-1 and = 65 nm for the bottom surface. The surface mobility enhancement is consistent with the longer mean free path of the nontrivial topological Dirac state. The surface contribution to the total conductance (Gs/Gtot = 84.8%) was consistent with the results obtained from the thickness dependence of conductance. Take the sheet carrier density into account, n = ns + nb t [44]. The mobility of the bulk channel was 12 cm2/Vs, which is close to the total Hall mobility of the 140-ÃŽ ¼m thick BSTS specimen, 13 cm2/Vs. The low Hall mobility of bulk carriers causes less interference with the surface Dirac fermions; thus, the enhancement of the surface contribution and quantum oscillations was detected in the specimens used in this study. Figure 4.5. (a) Temperature dependence of resistance. à ¯Ã†â€™Ã‚ ³Rxx is function of 1/B. n = 4, 5, and 6 are the LLs of the bottom surface; n = 6, 7, 8, and 9 are the LLs of the top surface of the 200-nm nanoflake. (b) Hall resistance versus magnetic field. The red dashed line is extended from the low B ( ±1T) fit. The inset shows the Fermi level positions of the top and bottom surfaces, respectively. BV is the bulk valance band, and BC is the conduction band. (c) The LL fan diagram plotted in 1/B versus the nth oscillation minima in the à ¯Ã†â€™Ã‚ ³Rxx. (d) The fit of temperature dependence of the SdH oscillation amplitude to the LK theory. (e) à ¯Ã†â€™Ã‚ ³R versus 1/B. The black curve is the experimental data, and the red curve is the fit to LK theory. 4.3.4 Weak anti-localization effect In addition to SdH oscillations, the helical surface state was further probed using the WAL effect on the 200-nm BSTS. The WAL effect in TIs originated from the  ° Berry phase, in which the probability of backscattering was suppressed as a result of the destructive interference of time-reversed paths. The angle field dependence magnetoconductance analysis is shown in Figure 4.6 (a). The sharp cusps of the magnetoconductance in the lower field region are features of WAL. The 2D nature of Dirac fermions associated with the  ° Berry phase, which is dependent only on the perpendicular component of the applying field, was obtained by subtracting the background from the 3D bulk WAL contribution, ΔGxx(ÃŽ ¸,B) = Gxx(ÃŽ ¸,B) Gxx(90 °,B) (5), as shown in Figure 4.6 (b). Figure 4.6 (b) shows that low-angle data merge into a single universal curve [15]. The Hikami-Larkin-Nagaoka (HLN) [15] model is used to calculate sheet conductance [27], as given in Eq. (3): , (4.3) where Gxx is sheet conductance, is the phase coherent length, and is the digamma function. The value for à ¯Ã‚ Ã‚ ¡ (-0.96) and (121 nm) were obtained for the 200-nm nanoflake. For the WAL effect in TIs, the prefactor à ¯Ã‚ Ã‚ ¡ was equal to -0.5 for a single surface state [40]. The complicacies of topological surface states resulted in an experimental value à ¯Ã‚ Ã‚ ¡ between -0.4 to -1.5 [38, 40]. In this study, the value à ¯Ã‚ Ã‚ ¡ = -0.96 indicated the existence of two surface states. Figure 4.6. (a) The angle field dependence magnetoconductance of the 200-nm nanoflake. The inset is a schematic diagram of the measurement. (b) ΔGxx versus the perpendicular field component (B cos ÃŽ ¸) for various angles. Low-angle data merge into a single curve (the green dashed line) fitted using the HLN model. 4.4 Conclusion In this study, dominated surface transport was observed in BSTS nanoflakes. The thickness dependence electrical transport and the SdH oscillations illustrated that the surface states in the 200-nm BSTS nanoflake contribute to nearly 90 % of the conductance. The achievement of the surface-dominated transport is mainly attributed to the high surface mobility relative to the bulk channel. The observation of SdH oscillations provides clear evidence of surface Dirac fermions. Surface-dominated transport was further confirmed by the WAL effect showing 2D nature of helical Dirac surface states. Moreover, electrical transport transforms from semiconducting to metallic behavior, and mobility was enhanced when the thickness decreased, indicating that surface states plays a crucial role in the thin film limit. The high-insulating bulk state in BSTS nanoflakes provides opportunities for future quantum computation and spintronics applications.

Technology Transfers: Developing Renewable Energy Sources Essay

Technology Transfers: Putting Theory into Practice Climate change is an increasingly demanding issue as global population continues to grow, energy sources are being depleted and cooperation between actors to take action is often difficult to enforce. Renewable energy is a growing technology. With the depletion of fossil fuels as well as increased greenhouse gases in the atmosphere due to fossil fuel burning, energy dependency will have to shift to renewable technologies such as solar photovoltaic, wind, hydroelectric and geothermal. Unfortunately, these technologies are expensive and building new or altering old plants to allow for their use is costly. Because developing countries are in transition and have a growing energy demand, their building of new energy facilities should logically incorporate and implement the new, cleaner technology. Most countries do not have the funds to support the new technology and so resort to purchasing old, inefficient parts from firms in developed countries that have already adjusted their technolog y. The Kyoto Protocol calls for increased energy efficiency and use of renewable energy sources as well as limiting emissions of greenhouse gases (UNIDO, 3). Each Annex I country is expected to adhere to reduction commitments while developing countries are not obligated to specific commitments, they still must report their progress and are encouraged to begin reductions of emissions where possible (Cullet, 168). In order to encourage developed countries' emission reductions of greenhouse gases, flexible mechanisms were instituted under the Kyoto Protocol, such as the Cleaner Development Mechanism or Joint Implementation. Cleaner Development Mechanisms involve one country with commitments an... ...s 11: 3, 1-30. Cullet, Philippe. 1999. Equity and Flexibility Mechanisms in the Climate Change Regime: Conceptual and Practical Issues. Review of European Community and International Environmental Law 8:2, 168. Duic, Neven, Luis M. Alves and Maria da Graca Carvalho. 2001. Potential of Kyoto Protcol in Transfer of Energy Technologies to Insular Countries. Transactions of Famena 25: 2, 27-37. Lash III, William H. 2000. The Kyoto Climate Change Treaty. Society 37: 4, 43-49. Renewable Energy Technology and Kyoto Protocol Mechanisms. 2003. European Commission. European Commuities, Belgium, pp 6- 30. Service Module 6: Sustainable Energy and Climate Change Overview. Online. United Nations Industrial Development Organization. Available:  HYPERLINK "http://www.unido.org/oc/5071. Updated 2004"
http://www.unido.org/oc/5071. Updated 2004. [Accessed May 2004]. Technology Transfers: Developing Renewable Energy Sources Essay Technology Transfers: Putting Theory into Practice Climate change is an increasingly demanding issue as global population continues to grow, energy sources are being depleted and cooperation between actors to take action is often difficult to enforce. Renewable energy is a growing technology. With the depletion of fossil fuels as well as increased greenhouse gases in the atmosphere due to fossil fuel burning, energy dependency will have to shift to renewable technologies such as solar photovoltaic, wind, hydroelectric and geothermal. Unfortunately, these technologies are expensive and building new or altering old plants to allow for their use is costly. Because developing countries are in transition and have a growing energy demand, their building of new energy facilities should logically incorporate and implement the new, cleaner technology. Most countries do not have the funds to support the new technology and so resort to purchasing old, inefficient parts from firms in developed countries that have already adjusted their technolog y. The Kyoto Protocol calls for increased energy efficiency and use of renewable energy sources as well as limiting emissions of greenhouse gases (UNIDO, 3). Each Annex I country is expected to adhere to reduction commitments while developing countries are not obligated to specific commitments, they still must report their progress and are encouraged to begin reductions of emissions where possible (Cullet, 168). In order to encourage developed countries' emission reductions of greenhouse gases, flexible mechanisms were instituted under the Kyoto Protocol, such as the Cleaner Development Mechanism or Joint Implementation. Cleaner Development Mechanisms involve one country with commitments an... ...s 11: 3, 1-30. Cullet, Philippe. 1999. Equity and Flexibility Mechanisms in the Climate Change Regime: Conceptual and Practical Issues. Review of European Community and International Environmental Law 8:2, 168. Duic, Neven, Luis M. Alves and Maria da Graca Carvalho. 2001. Potential of Kyoto Protcol in Transfer of Energy Technologies to Insular Countries. Transactions of Famena 25: 2, 27-37. Lash III, William H. 2000. The Kyoto Climate Change Treaty. Society 37: 4, 43-49. Renewable Energy Technology and Kyoto Protocol Mechanisms. 2003. European Commission. European Commuities, Belgium, pp 6- 30. Service Module 6: Sustainable Energy and Climate Change Overview. Online. United Nations Industrial Development Organization. Available:  HYPERLINK "http://www.unido.org/oc/5071. Updated 2004"
http://www.unido.org/oc/5071. Updated 2004. [Accessed May 2004].

The Current “Age of Accountability” Law in Light of Developmental Psychology Current Law Upheld Case Study

In the case study provided, one can see many areas where the development of the child in question can be taken into consideration when looking at the case from a law standpoint. In any case involving children, one must always take into account their environment, their developmental age, and their true age. With each age group, there is a norm for development and each child must be evaluated regarding that norm. In this case, the current law regarding the â€Å"age of accountability† can be upheld through three basic points. These points are the biosocial, the cognitive, and the psychosocial areas of development. Each area plays a huge role in whether or not a child (at the age of six) can be held accountable for such a violent act. In the area of biosocial development, everything from a child’s nutrition to brain development to abuse can affect their perceptions (Berger, 2008). In the case provided, the six year old boy, coming from a single parent household, could very easily suffer developmentally in this area. Historically, single parent households make much less than households where both parents are present. Less income (socioeconomic status decline) could equal less nutritious food to aid in proper development. At the age of the child provided for this case study, he seems to be at the norm for brain development. At this age, even though children can think in rapid succession, they do not process the information to the point of seeing the true consequences. The child is also not completely able to use deductive reasoning when thinking the situation through from beginning to end and vice versa (Berger, 2008). Emotions at this point also play a key role in the development of the child provided. At this age, emotions such as anger (which would commonly be felt after the scuffle on the playground) can grow over a few hours and especially overnight, in a child who has anger or guilt problems anyway. While anger is a normal emotion, some children at this age struggle with the appropriate way to deal with it and lash out, resulting in injury. Taking into consideration the lifestyle of the juvenile in question, abuse and/or neglect could also be a large problem in his dealing with anger issues. While he may see the maltreatment he could be receiving as just basic attention, he is unable to process the true impact of the situation at his age (Berger, 2008). When the child sees anger at home, he is more likely to engage in anger motivated activities outside the home. Cognitive development of the six year old boy must also be taken into consideration when upholding the age of accountability law. Due to the fact that children of this age tend to be very self-centered and have the ability to focus on one idea (regardless of perception), a child with anger issues will see their problem is the whole world and that that one focal point is to stop the angry feeling (Berger, 2008). While to an adult this is irrational thought since the consequences are not planned for, to a child this creates harmony in their world of â€Å"me. Social learning at this age is a huge influence on how they react to their environment. In the case provided, the child is reacting the only way he knows how. Since both his father and grandfather are in the corrections system for gun related charges, it is likely that the child is only modeling the behavior he feels is set forth by those before him (Berger, 2008). While the child does not realize what he is doing at the time, he is an apprentice in thinking in the same way the other male figures have acted in his life. Even though the child has a male influence in his life (his uncle), it does not seem to be constructive as the uncle is likely the one who left the gun out irresponsibly. To uphold the current law, it should also be taken into consideration that a child at this age is merely attempting to make the difference between belief and reality. What a child sees on television and plays in video games can also play a role in their perception of the world as well as their cognitive and psychological development (Berger, 2008). Children before the age of seven have a difficult time realizing the reality and the fantasy within their environment. To them, a violent act is just the means to the end, the consequences are not their concern, and their goal is to end their own suffering regardless of the cost due to their self-centeredness. In the area of psychosocial development, a child should not be held accountable at the age of six due to their emotional status, ability to receive and internalize emotion, and falling victim to their parents’ style of parenting (Berger, 2008). If a child is subjected to authoritarian parenting, they are more likely to be less happy, suffer from depression, and feel guilty about situations in their environment. In the case presented, this could very well be the case for the child as his reason for extreme anger could be internalizing guilt for his father and grandfather being out of his life and in prison. Permissive parenting could also be a cause of developmental issue in a child of this age as they would be lacking of self control and unhappy. Again, the media begins to play a role in the lives of children this age. When a child observes violence and hatred, then they will most likely exude this type of behavior as well if it does not go corrected by a parent (Berger, 2008). When the media is the â€Å"parent† of the child, television used as a babysitter, the only role model they have are the actors on television to mimic and model their behavior. Overall, based on the information provided by Berger in the text, the law regarding whether or not the child in the case from Michigan should be held accountable should be upheld. It can be seen from the information provided above that the child is not developed enough to weigh the consequences of their actions and are most likely victims to their environment. Children cannot control what they are shown and thus at age six should not be accountable for their violent actions when they do not understand what the repercussions of their action could be and do not understand something as complex as taking another life.

Italian Verb Conjugations Godere